MacLaurin Series (DP IB Maths: AA HL)

Exam Questions

5 hours24 questions
1a
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4 marks

Consider the general Maclaurin series formula

 space f open parentheses x close parentheses equals f open parentheses 0 close parentheses plus x f to the power of apostrophe open parentheses 0 close parentheses plus fraction numerator x squared over denominator 2 factorial end fraction f to the power of apostrophe apostrophe end exponent open parentheses 0 close parentheses plus   horizontal ellipsis   plus fraction numerator x to the power of n over denominator n factorial end fraction f to the power of open parentheses n close parentheses end exponent open parentheses 0 close parentheses plus   horizontal ellipsis

(wherespace f to the power of open parentheses n close parentheses end exponent indicates the n to the power of t h end exponentderivative ofspace f).

Use the formula to find the first five terms of the Maclaurin series for e to the power of 2 x end exponent.

1b
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2 marks

Hence approximate the value of e to the power of 2 x end exponent when x equals 1.

1c
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3 marks
(i)
Compare the approximation found in part (b) to the exact value of e to the power of 2 x end exponent when x equals 1.

(ii)
Explain how the accuracy of the Maclaurin series approximation could be improved.

1d
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2 marks

Use the general Maclaurin series formula to show that the general term of the Maclaurin series for e to the power of 2 x end exponent is 

fraction numerator open parentheses 2 x close parentheses to the power of n over denominator n factorial end fraction

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2a
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3 marks

Use substitution into the Maclaurin series for sin space x

sin space x equals x minus fraction numerator x cubed over denominator 3 factorial end fraction plus fraction numerator x to the power of 5 over denominator 5 factorial end fraction minus   horizontal ellipsis 

to find the first four terms of the Maclaurin series for sin space open parentheses x over 2 close parentheses.

2b
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3 marks

Hence approximate the value of sin space pi over 2 and compare this approximation to the exact value.

2c
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2 marks

Without performing any additional calculations, explain whether the answer to part (a) would be expected to give an approximation of sin space pi over 4 that is more accurate or less accurate than its approximation for sin pi over 2.

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3a
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4 marks

The Maclaurin series for e to the power of xand sin space x are

e to the power of x equals 1 plus x plus fraction numerator x squared over denominator 2 factorial end fraction plus   horizontal ellipsis blank and          sin space x equals x minus fraction numerator x cubed over denominator 3 factorial end fraction plus fraction numerator x to the power of 5 over denominator 5 factorial end fraction minus   horizontal ellipsis

Find the Maclaurin series for e to the power of x s i n space x up to and including the term in x to the power of 4.

3b
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3 marks

Use the Maclaurin series for sin space x, along with the fact that   fraction numerator straight d over denominator straight d x end fraction open parentheses sin space x close parentheses equals cos space x,  to find the first four terms of the Maclaurin series for cos space x.

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4a
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4 marks

Use the general Maclaurin series formula to find the first four terms of the Maclaurin series for  fraction numerator 1 over denominator 1 plus x end fraction.

4b
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3 marks

Confirm that the answer to part (a) matches the first four terms of the binomial theorem expansion of ​ fraction numerator 1 over denominator 1 plus x end fraction .

4c
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2 marks

The Maclaurin series for ln space left parenthesis 1 plus x right parenthesis is 

ln open parentheses 1 plus x close parentheses equals x minus x squared over 2 plus x cubed over 3 minus   horizontal ellipsis

Differentiate the Maclaurin series for ln space left parenthesis 1 plus x right parenthesis up to its fourth term and compare this to the answer from part (a). Give an explanation for any similarities that are found.

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5a
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3 marks

Use the Maclaurin series for sin space x and cos space x to find a Maclaurin series approximation for 2 space sin space x space cos space x up until the term in x to the power of 4.

5b
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3 marks

The double angle identity for sine tells us that 

sin space 2 x equals 2 space sin space x space cos space x

Use substitution into the Maclaurin series for sin space x to find a Maclaurin series approximation for sin space 2 x up until the term in x to the power of 4, and confirm that this matches the answer to part (a).

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6a
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4 marks

Use the Binomial theorem to find a Maclaurin series for the functionspace f defined by 

space f open parentheses x close parentheses equals square root of 1 minus 2 x squared end root

Give the series up to and including the term in x to the power of 6.

6b
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2 marks

State any limitations on the validity of the series expansion found in part (a).

6c
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4 marks

Use the answer to part (a) to estimate the value of square root of 0.5 end root, and compare the accuracy of that estimated value to the actual value of square root of 0.5 end root.

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7a
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4 marks

Consider the differential equation 

y to the power of apostrophe equals 2 y squared plus x

together with the initial condition y left parenthesis 0 right parenthesis equals 1.

(i)
Show that y double apostrophe equals 4 y y to the power of apostrophe plus 1.

(ii)
Use an equivalent method to find expressions for y to the power of apostrophe apostrophe apostrophe end exponent, y to the power of left parenthesis 4 right parenthesis end exponent and y to the power of open parentheses 5 close parentheses end exponent. Each should be given in terms of y and of lower-order derivatives of y.
7b
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3 marks

Using the boundary condition above, calculate the values of y to the power of apostrophe open parentheses 0 close parentheses, y to the power of apostrophe apostrophe end exponent open parentheses 0 close parentheses, y to the power of apostrophe apostrophe apostrophe end exponent open parentheses 0 close parentheses, y to the power of open parentheses 4 close parentheses end exponent open parentheses 0 close parentheses and y to the power of open parentheses 5 close parentheses end exponent open parentheses 0 close parentheses.

7c
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4 marks

Let space f left parenthesis x right parenthesis be the solution to the differential equation above with the given boundary condition, so that y equals f left parenthesis x right parenthesis.

Using the answers to part (b), find the first six terms of the Maclaurin series for space f left parenthesis x right parenthesis.

7d
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2 marks

Hence approximate the value of to 4 d.p. when x equals 0.1.

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8a
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5 marks

Consider the differential equation

y to the power of apostrophe equals 2 x y squared

with the initial condition y left parenthesis 0 right parenthesis equals 1.

(i)
Find y to the power of apostrophe apostrophe end exponent.

(ii)
Hence show that y to the power of apostrophe apostrophe apostrophe end exponent equals 8 y y to the power of apostrophe plus 4 x open parentheses y to the power of apostrophe close parentheses squared plus 4 x y y to the power of apostrophe apostrophe end exponent  and  y to the power of open parentheses 4 close parentheses end exponent equals 12 open parentheses y to the power of apostrophe close parentheses squared plus 12 y y to the power of apostrophe apostrophe end exponent plus 12 x y to the power of apostrophe y to the power of apostrophe apostrophe end exponent plus 4 x y y to the power of apostrophe apostrophe apostrophe end exponent
8b
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4 marks

Use the results from part (a) along with the given initial condition to find a Maclaurin series to approximate the solution of the differential equation, giving the approximation up to the term in x to the power of 4.

8c
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4 marks

Use separation of variables to show that the exact solution of the differential equation with the given initial condition is 

y equals fraction numerator 1 over denominator 1 minus x squared end fraction

8d
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3 marks

Use the binomial theorem to find an approximation for ​ fraction numerator 1 over denominator 1 minus x squared end fraction up to the term in x to the power of 4, and verify that it matches the answer to part (b).

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1a
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2 marks

Consider the general Maclaurin series formula

f left parenthesis x right parenthesis equals f open parentheses 0 close parentheses plus x f apostrophe open parentheses 0 close parentheses plus fraction numerator x squared over denominator 2 factorial end fraction f double apostrophe open parentheses 0 close parentheses plus... plus fraction numerator x to the power of n over denominator n factorial end fraction f to the power of open parentheses n close parentheses end exponent open parentheses 0 close parentheses plus...

(where f to the power of open parentheses n close parentheses end exponent indicates the n to the power of t h end exponent derivative of f).

Explain why the formula cannot be used to calculate a Maclaurin expansion for ln space x.

1b
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4 marks

Use the formula to find the first five non-zero terms of the Maclaurin series for ln left parenthesis 1 plus x right parenthesis.

1c
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4 marks

Hence approximate the value of ln space 2.

(i)
by substituting the value x equals 1

(ii)
by substituting the value x equals negative 1 half.
1d
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4 marks
(i)
Compare the approximations found in part (c) to the exact value of ln space 2.

(ii)
Explain briefly the reason for the difference in accuracy between the two approximations.
1e
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3 marks

Use the general Maclaurin series formula to show that the general term of the Maclaurin series for ln open parentheses 1 plus x close parentheses is

fraction numerator open parentheses negative 1 close parentheses to the power of n plus 1 end exponent x to the power of n over denominator n end fraction comma space space space space space space space space space space n greater or equal than 1

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2a
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3 marks

Find the first four non-zero terms of the Maclaurin series for cos space 4 x in ascending powers of x.

2b
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3 marks

Hence approximate the value of cos space 3 and compare this approximation to the exact value.

2c
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1 mark

Explain how the accuracy of the Maclaurin series approximation in part (b) could be improved.

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3a
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5 marks

Find the Maclaurin series for e to the power of 2 x end exponent ln open parentheses 1 plus x close parentheses   in ascending powers of x, up to and including the term in x to the power of 4.

3b
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3 marks

Hence find the first four terms of the Maclaurin series for e to the power of 2 x end exponent open parentheses 2 ln open parentheses 1 plus x close parentheses plus fraction numerator 1 over denominator 1 plus x end fraction close parentheses in ascending powers of x.

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4a
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4 marks

Use the general Maclaurin series formula to find the first four terms of the Maclaurin series for fraction numerator 1 over denominator 2 plus 3 x end fraction  in ascending powers of x.

4b
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3 marks

Confirm that the answer to part (a) matches the first four terms of the binomial theorem expansion of fraction numerator 1 over denominator 2 plus 3 x end fraction .

4c
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3 marks

Find the Maclaurin series for ln open parentheses 2 plus 3 x close parentheses in ascending powers of x, up to and including the term in x to the power of 4.

4d
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3 marks

Find the derivative of ln left parenthesis 2 plus 3 x right parenthesis , and confirm that the series found in parts (a) and (c) reflect the relationship between ln open parentheses 2 plus 3 x close parentheses and fraction numerator 1 over denominator 2 plus 3 x end fraction that is thereby implied.

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5a
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3 marks
(i)
Write down the first five non-zero terms of the Maclaurin series for arctan space x in ascending powers of x.

(ii)
Hence find an approximation for the value of the integral
integral subscript 0 superscript 1 arctan space x space d x
5b
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4 marks

Use integration by parts to show that

integral arctan space x space d x equals x space arctan space x minus 1 half ln open parentheses 1 plus x squared close parentheses plus c
5c
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3 marks

Hence determine the exact value of  integral subscript 0 superscript 1 arctan space x space d x, and compare it to the approximation found in part (a)(ii).

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6a
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4 marks

Use the binomial theorem to find a Maclaurin series for the function f defined by

f open parentheses x close parentheses equals square root of 4 minus 9 x squared end root 

Give the series in ascending powers of x up to and including the term in x to the power of 6.

6b
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2 marks

State any limitations on the validity of the series expansion found in part (a).

6c
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4 marks

Use the answer to part (a) to estimate the value of square root of 3.91 end root , and compare the accuracy of that estimated value to the actual value of  square root of 3.91 end root.

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7a
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4 marks

Consider the differential equation

y apostrophe equals x squared minus 3 y squared 

together with the initial condition y open parentheses 0 close parentheses equals 1 . 

Find expressions for y double apostrophe comma space y apostrophe apostrophe apostrophe comma space y to the power of open parentheses 4 close parentheses end exponent and y to the power of open parentheses 5 close parentheses end exponent . Each should be given in terms of x and y and of lower-order derivatives of y.

7b
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7 marks

Let f open parentheses x close parentheses be the solution to the differential equation above with the given boundary condition, so that y equals f open parentheses x close parentheses. 

Find the first six terms in ascending powers of x  of the Maclaurin series for f open parentheses x close parentheses.

7c
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2 marks

Hence approximate the value of y when x equals 0.1.

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8a
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9 marks

Consider the differential equation

 y apostrophe equals negative 2 x y

with the initial condition y open parentheses 0 close parentheses equals 2. 

By first finding expressions for y double apostrophe comma space y apostrophe apostrophe apostrophe comma space y to the power of open parentheses 4 close parentheses end exponent comma space y to the power of open parentheses 5 close parentheses end exponent and y to the power of open parentheses 6 close parentheses end exponent in terms of x comma space y and lower-order derivatives of y,  find a Maclaurin series for the solution to the differential equation with the given boundary condition, in ascending powers of xup to and including the term in x to the power of 6.

8b
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4 marks

Solve the differential equation with the given boundary condition analytically to find an exact solution in the form y equals f open parentheses x close parentheses.

8c
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3 marks

Find the first four non-zero terms of the Maclaurin series for the answer to part (b), and confirm that they match those in the answer to part (a).

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1a
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6 marks

Find the first three non-zero terms of the Maclaurin series for tan space x in ascending powers of x.

1b
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2 marks

Confirm that the result from part (a) gives the same type of function – either even or odd – as tan space x.

 

1c
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4 marks

Hence approximate the value of tan space 1

(i)
by substituting the value x equals 1
(ii)
by substituting another positive value of x .

 

1d
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4 marks
(i)
Compare the approximations found in part (c) to the exact value of tan space 1.

(ii)
Explain briefly the reason for the difference in accuracy between the two approximations.

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2a
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4 marks

Find the first four non-zero terms of the Maclaurin series for e to the power of negative 2 x end exponent in ascending powers of x.

2b
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3 marks

Hence approximate the value of square root of e and compare this approximation to the exact value.

2c
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1 mark

Explain how the accuracy of the Maclaurin series approximation in part (b) could be improved.

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3a
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5 marks

Find the Maclaurin series for e to the power of x open parentheses sin space 3 x plus cos square root of x close parentheses in ascending powers of x, up to and including the term in x cubed.

3b
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4 marks

Hence find the first three non-zero terms, in ascending powers of x, of the Maclaurin series for

e to the power of x open parentheses 2 space sin space 3 x plus 6 space cos space 3 x plus 2 space cos square root of x minus fraction numerator sin square root of x over denominator square root of x end fraction close parentheses

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4a
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5 marks

Consider the function f defined by f open parentheses x close parentheses equals e to the power of 3 x end exponent cos space 2 x .

Show that  f apostrophe apostrophe open parentheses x close parentheses equals p f open parentheses x close parentheses plus p f apostrophe open parentheses x close parentheses, where p and q are constants to be determined.

4b
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3 marks

Hence find the Maclaurin series for f open parentheses x close parentheses  in ascending powers of x, up to and including the term in x to the power of 5.

4c
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7 marks

Show that integral f open parentheses x close parentheses d x equals e to the power of 3 x end exponent over 13 open parentheses 2 space sin space 2 x plus 3 space cos space 2 x close parentheses plus c.

4d
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4 marks

Hence find the first seven terms, in ascending powers of x, of the Maclaurin series for e to the power of 3 x end exponent open parentheses 2 space sin space 2 x plus 3 space cos space 2 x close parentheses.

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5a
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4 marks

Find the Maclaurin series for e to the power of 1 half x squared end exponent in ascending powers of x, up to and including the term in x to the power of 8.

5b
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3 marks

The probability density function for the random variable X tilde straight N open parentheses 0 comma 1 close parentheses is 

f open parentheses x close parentheses equals fraction numerator 1 over denominator square root of 2 straight pi end root end fraction e to the power of negative 1 half x squared end exponent

Use the result of part (a) to find an approximation for the probability straight P left parenthesis 0 less or equal than X less or equal than 1 right parenthesis.

5c
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3 marks

Determine the percentage error of your approximation from part (b).

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6
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9 marks

Consider the function f defined by

 f open parentheses x close parentheses equals fraction numerator 1 over denominator square root of 1 minus 2 x squared end root end fraction 

By first determining the Maclaurin series of f open parentheses x close parentheses in ascending powers of x,  up to and including the term in x to the power of 6 , show that

sin straight pi over 4 almost equal to 0.70710675 

Be sure to justify that the Maclaurin series is valid for the value of x used to produce your approximation.

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7a
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5 marks

Consider the differential equation

 y apostrophe equals cos space x plus x y squared 

together with the initial condition y open parentheses 0 close parentheses equals 1. 

Find expressions for y double apostrophe comma space y apostrophe apostrophe apostrophe comma space y to the power of open parentheses 4 close parentheses end exponent and y to the power of open parentheses 5 close parentheses end exponent.  Each should be given in terms of x and y and of lower-order derivatives of y.

7b
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7 marks

Let f open parentheses x close parentheses  be the solution to the differential equation above with the given boundary condition, so that y equals f open parentheses x close parentheses . 

Find the first six terms in ascending powers of x of the Maclaurin series for f open parentheses x close parentheses.

7c
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2 marks

Hence find an approximation for the value of y when x equals 0.1.

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8a
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9 marks

Consider the differential equation

 y apostrophe equals fraction numerator y over denominator x plus 1 end fraction plus 1 comma space space space space space space space space space space space space space x greater than negative 1 

with the initial condition y open parentheses 0 close parentheses equals negative 1 . 

By first finding expressions for y double apostrophe comma space y apostrophe apostrophe apostrophe comma and y to the power of open parentheses 4 close parentheses end exponent in terms of x comma space y  and lower-order derivatives of y,  find a Maclaurin series for the solution to the differential equation with the given boundary condition, in ascending powers of x  up to and including the term in x to the power of 4.

8b
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5 marks

Solve the differential equation with the given boundary condition analytically to find an exact solution in the form y equals f open parentheses x close parentheses.

8c
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3 marks

Find the first four non-zero terms of the Maclaurin series for the answer to part (b), and confirm that they match those in the answer to part (a).

 

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