Polynomial Functions (DP IB Maths: AA HL)

Exam Questions

4 hours32 questions
1a
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2 marks

Below is the graph of a function f left parenthesis x right parenthesis equals a x cubed plus b x squared plus c x plus d,  passing through the points Pleft parenthesis negative 3 comma 0 right parenthesis, Qleft parenthesis negative 2 comma 0 right parenthesis, Rstretchy left parenthesis 1 half comma space 0 stretchy right parenthesis and Sleft parenthesis 2 comma space 60 right parenthesis.q1a_2-7_ib-aa-hl-maths

a)
Find the values of a comma space b comma space c and d.
1b
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4 marks

The function is translated vertically by the vector open parentheses table row 0 row k end table close parentheses so that it passes through the point left parenthesis 3 comma 190 right parenthesis.  

b)
Find the value of k.

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2a
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2 marks
a)
Given that the equation 2 x squared plus 4 x minus m equals 0 has two real solutions, find the set of possible values of m.
2b
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2 marks
b)
Given that the function f left parenthesis x right parenthesis equals x squared minus 5 x plus 2 c has repeated roots, find c.
2c
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4 marks
c)
Given that the function g left parenthesis x right parenthesis equals 2 x squared plus 2 k x plus stretchy left parenthesis 3 over 2 minus k stretchy right parenthesis has no real roots, find the set of possible values of k.

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3
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6 marks

Let a function f be defined by f left parenthesis x right parenthesis equals 2 x cubed plus 7 x squared minus 3 x minus 18

(i)
Show that left parenthesis x plus 3 right parenthesis is a factor of f left parenthesis x right parenthesis.

(ii)
Hence factorise f left parenthesis x right parenthesis fully.

(iii)
Write down all the solutions to 2 x cubed plus 7 x squared minus 3 x minus 18 equals 0.

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4a
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4 marks
a)
Factorise fully 6 x cubed plus x squared minus 12 x plus 5.

4b
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7 marks
b)
f left parenthesis x right parenthesis equals a x cubed plus left parenthesis 5 a minus 2 right parenthesis x squared plus left parenthesis 4 a plus 2 right parenthesis x minus 2 a 

(i)
Given that left parenthesis x plus 3 right parenthesis is a factor of f left parenthesis x right parenthesis, find a. 

(ii)
Hence factorise f left parenthesis x right parenthesis fully.

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5a
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2 marks

Consider the polynomial g left parenthesis x right parenthesis equals 3 x to the power of 5 minus 25 x to the power of 4 plus 72 x cubed minus 72 x squared minus 16 x plus 48.

a)
Show that 2 is a root of g left parenthesis x right parenthesis.
5b
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5 marks
b)
Given that 2 is a root of g open parentheses x close parentheses with multiplicity 3, factorise g open parentheses x close parentheses fully and hence state the other two roots.

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6
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5 marks

Consider the function f left parenthesis x right parenthesis equals 4 x cubed plus 6 x squared minus 7 x plus 2.

(i)
Find the quotient and remainder when 4 x cubed plus 6 x squared minus 7 x plus 2 is divided by left parenthesis x minus 2 right parenthesis. 

(ii)
Hence write  4 x cubed plus 6 x squared minus 7 x plus 2 in the form left parenthesis x minus 2 right parenthesis left parenthesis a x squared plus b x plus c right parenthesis plus d comma where a comma space b comma space c and d are constants to be determined.

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7a
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5 marks

The function f left parenthesis x right parenthesis equals 2 x cubed minus 5 x squared plus a x plus b  has left parenthesis 2 x plus 3 right parenthesis as a factor, and when f left parenthesis x right parenthesis is divided by left parenthesis x minus 2 right parenthesis the remainder is 7. 

a)
Show that a and b must satisfy the simultaneous equations:  

2 a plus b equals 11

3 a minus 2 b equals negative 36

7b
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2 marks
b)
Hence find a and b.

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8
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5 marks

Given that 3 plus 2 i is one of the roots of the equation x cubed minus 3 x squared minus 5 x plus 39 equals 0 comma find the other two roots.

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9a
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5 marks
a)
For each of the following polynomials, find the sum of the roots and the product of the roots. 

(i)
space f left parenthesis x right parenthesis equals 9 x to the power of 4 plus 7 x cubed minus 3 x plus 2
 
(ii)
g left parenthesis x right parenthesis equals 7 x to the power of 5 minus x to the power of 4 plus 2 x cubed plus x squared minus 5 x plus 14 

(iii)
h left parenthesis x right parenthesis equals 2 x cubed minus 5 x squared minus 3 x 

(iv)
space j left parenthesis x right parenthesis equals negative 3 x to the power of 4 plus 2 x squared plus 5 x minus 3
9b
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5 marks
b)
Consider the equation 6 x cubed minus left parenthesis 4 a right parenthesis x squared minus left parenthesis a plus 2 right parenthesis x equals 0
 
Given that the sum of the roots is 8 over 3, find the three roots of the equation.

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10
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4 marks

For the function  f left parenthesis x right parenthesis equals a x to the power of 4 plus b x cubed minus x squared minus 24 x minus left parenthesis 5 b plus 1 right parenthesis,  the sum of the roots is begin mathsize 16px style fraction numerator negative 7 over denominator 2 end fraction end style and the product of the roots is negative 18.  Find the values of a and b.

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11a
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2 marks

The functionspace f left parenthesis x right parenthesis equals left parenthesis x minus 3 right parenthesis left parenthesis x squared plus 3 x minus 4 right parenthesis left parenthesis a x squared plus b x plus c right parenthesis has three real and two complex roots. 

a)
Find the three real roots.

11b
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5 marks

It is given forspace f left parenthesis x right parenthesis that the sum of the roots is negative 3 over 2 and the product of the roots is negative 60

b)
Find the two complex roots, giving your answers in exact form.

11c
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4 marks
c)
Given thatspace f left parenthesis 2 right parenthesis equals negative 144, find the values of a comma space b and c.

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12a
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2 marks

 alphaandspace beta are non-real roots of the equation x squared plus 3 k x plus 2 k plus 1 equals 0,  where k greater than 0 is a constant. 

a)
Find alpha plus beta and alpha beta, in terms of k.
12b
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2 marks
b)
Given that alpha squared plus beta squared equals 3, show that left parenthesis alpha plus beta right parenthesis squared equals 4 k plus 5.
12c
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3 marks
c)
Hence find the value of k .

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13a
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2 marks

Consider the function f left parenthesis x right parenthesis equals k x cubed plus 3 x squared plus 11 x plus 3 k,  where k is a constant.

It is given that open parentheses 2 x minus 1 close parentheses is a factor of f left parenthesis x right parenthesis

(a)
Find the value of k.
13b
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3 marks
(b)
Fully factorise f left parenthesis x right parenthesis.
13c
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3 marks
(c)
Hence sketch the graph of y equals f left parenthesis x right parenthesis . Clearly label the coordinates of any points where the graph intersects the coordinate axes.

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1a
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4 marks

Consider the function f open parentheses x close parentheses equals 3 x cubed plus p x squared plus 22 x plus q,  where p and q are constants.  It is given that left parenthesis x squared minus x plus 6 right parenthesis is a factor of f open parentheses x close parentheses.

(a)
Find the values of p and q.
1b
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3 marks
(b)
Find the roots of f open parentheses x close parentheses.

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2a
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5 marks

3 over 4 is a zero of the function f open parentheses x close parentheses equals 4 x cubed minus 19 x squared plus k x minus 12 comma where k is a constant.

(a)
As well as finding the value of k , find all the solutions to the equation f open parentheses x close parentheses equals 0.
2b
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3 marks
(b)
Sketch the graph of  y equals f open parentheses x close parentheses.
2c
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2 marks

The point open parentheses 7 over 6 comma 125 over 108 close parentheses  is a turning point on the graph y equals f open parentheses x close parentheses.

(c)
Given that f open parentheses x close parentheses equals p  has three distinct real solutions, where p is a real constant, find the set of possible values of p.

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3a
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3 marks

The graph of y equals f open parentheses x close parentheses is shown below, where f open parentheses x close parentheses is a polynomial function. The graph passes through the points straight A open parentheses negative 3 comma 0 close parentheses comma space straight B open parentheses 1 half comma 0 close parentheses spaceand straight C open parentheses 1 comma negative 12 close parentheses.

q3a_2-7_polynomial-functions_hard_ib_aa_hl_maths-dig

(a)
Given that the degree of f is as small as possible, find an equation for f open parentheses x close parentheses.
3b
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3 marks

The graph is translated by the vector open parentheses table row k row 0 end table close parentheses  to form the graph y equals g open parentheses x close parentheses, where k is a constant and g open parentheses x close parentheses is a polynomial.

(b)
Given that is a factor of g open parentheses x close parentheses, find the possible values of k.

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4
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6 marks

Given that open parentheses x plus 4 close parentheses is a factor of the function f left parenthesis x right parenthesis equals p x cubed plus left parenthesis 5 p plus 1 right parenthesis x squared plus 5 q x minus 2 q minus 2 and that the remainder when f open parentheses x close parentheses  is divided by open parentheses x plus 1 close parentheses is negative 12,  find the values of the constants p and q.

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5
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4 marks

Show that 3 x cubed plus 16 x squared minus 22 x can be written in the form left parenthesis 3 x plus 1 right parenthesis left parenthesis a x squared plus b x plus c right parenthesis plus d comma where a comma space b comma space c and d are constants to be found.

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6
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6 marks

For the function f open parentheses x close parentheses equals open parentheses 3 x minus 1 close parentheses open parentheses x squared plus x minus 1 close parentheses open parentheses a x squared plus b x plus c close parentheses, the sum of the roots is 1 third and the product of the roots is negative 31 over 36.  Find all five roots of f open parentheses x close parentheses.

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7
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6 marks

alpha and beta are non-real solutions of the equation 2 x squared minus open parentheses 2 k minus 3 close parentheses x plus 2 k equals 0
Given that  alpha squared plus beta squared equals 9 over 4
 and k not equal to 0,  find the value of k.

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8
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6 marks

The function f open parentheses x close parentheses equals x squared minus m x plus 3 m minus 4 has two integer solutions, one of which is double the other one. 

Find the value of m.

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9a
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2 marks

Consider the function f open parentheses x close parentheses equals p x to the power of 6 plus q x to the power of 4 plus r x squared plus 1, where p comma space q spaceand r are real constants.

(a)
Show that if alpha is a zero of f open parentheses x close parentheses then negative alpha  is also a zero.
9b
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4 marks
(b)
Given that square root of 5  and negative 7 minus 6 straight i are roots of the equation f open parentheses x close parentheses equals 0, find the value of p.

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10a
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6 marks

Let f be a polynomial defined by f open parentheses x close parentheses equals 8 x cubed minus 24 x squared minus 72 x plus 385.

(a)
Use algebra to show that:
(i)
open parentheses 2 x plus 7 close parentheses is a factor of f open parentheses x close parentheses,
(ii)
f open parentheses x close parentheses equals 0 has exactly one real root.
10b
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3 marks

Consider the function g defined by g open parentheses x close parentheses equals f open parentheses x close parentheses plus k, where k is a real constant.

(b)
Given that the equation g open parentheses x close parentheses equals 0  has exactly three real roots, find the set of possible values of k.

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1a
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5 marks

Consider the function f open parentheses x close parentheses equals 2 x to the power of 6 minus 5 x to the power of 5 plus p x to the power of 4 plus q x cubed minus 2 x squared plus 20 x minus 8, where p and q are constants.  It is given that left parenthesis x squared minus x minus 2 right parenthesis is a factor of f open parentheses x close parentheses.

(a)
Show that p equals 8  and find the value of q.
1b
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6 marks
(b)
Given that negative 2 straight i is a root of f, find all of the roots of the equation f open parentheses x close parentheses equals 0.  .

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2a
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2 marks

Consider the function

f open parentheses x close parentheses equals sum from r equals 0 to n of a subscript r x to the power of r 

where a subscript r element of straight real numbers for r equals 0 comma space 1 comma space... comma space n

The graph of y equals f open parentheses x close parentheses, shown below, passes through straight A open parentheses 0 comma 18 close parentheses.  The roots of f open parentheses x close parentheses are 3 over 2 comma space minus 1 comma space straight i and negative straight i.

q2a_2-7_polynomial-functions_very_hard_ib_aa_hl_maths-diagram

(a)
Explain why n must be even.
2b
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4 marks
(b)
Given that n is as small as possible, find an equation for f open parentheses x close parentheses.

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3a
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4 marks

A polynomial function f is defined by f left parenthesis x right parenthesis equals k left parenthesis m minus x right parenthesis cubed left parenthesis n minus x right parenthesis ² where k comma space m and n are positive constants with n greater than m.

(a)
Sketch the graph of y equals f open parentheses x close parentheses. Label the coordinates where the graph crosses the coordinate axes.
3b
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1 mark
(b)
Determine the maximum number of distinct real solutions to the equation f open parentheses x close parentheses equals p, where p is a real constant.
3c
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3 marks

Consider the function g open parentheses x close parentheses equals f open parentheses a x plus b close parentheses, where a and b are positive constants. The points open parentheses 0 comma 0 close parentheses and open parentheses 1 comma 0 close parentheses lie on the graph y equals g open parentheses x close parentheses.

(c)
Find a and b in terms of m and n.

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4
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7 marks

Consider the function g defined by g left parenthesis x right parenthesis equals a x cubed plus 4 b x squared plus left parenthesis 4 a minus 3 right parenthesis x minus 3 b,  where a comma space b element of straight real numbers are constants.

Given that open parentheses x minus 3 close parentheses is a factor of g open parentheses x close parentheses, and that the sum of the roots of the equation g open parentheses x close parentheses equals 0 is 5, 

(i)
find the values of a and b, and
(ii)
hence factorise g open parentheses x close parentheses fully.

 

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5
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7 marks

Consider the function f  defined by  f open parentheses x close parentheses equals open parentheses 2 x cubed plus 9 x squared plus 4 x minus 15 close parentheses open parentheses m x squared plus n x plus p close parentheses,  where m comma space n spaceand p are real constants. 

It is given that the sum of the roots of the equation  f open parentheses x close parentheses equals 0 is  negative 41 over 6,  and that the product of the roots is 25 over 2. 

Find a set of values for m comma space n spaceand p that satisfies the above conditions, such that m comma space n comma space p space element of straight integer numbers. .

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6a
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7 marks

The equation x squared plus left parenthesis k minus 1 right parenthesis x minus 2 k equals 0 comma space k element of straight real numbers has non-real roots alpha and beta where  alpha cubed plus beta cubed equals 5

(a)
Find the value of k.
6b
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2 marks

The equation x squared plus p x plus q equals 0  has roots alpha cubed and beta cubed.

(b)
Find the values of p and q.

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7a
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2 marks

Consider the polynomial function defined by

f open parentheses x close parentheses equals sum from r equals 0 to 5 of a subscript r x to the power of r comma 

Where the a subscript r are real constants. The function has the property that f open parentheses negative x close parentheses equals negative f open parentheses x close parentheses for all values of x

(a)
Show that  a subscript 0 equals a subscript 2 equals a subscript 4 equals 0.

7b
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6 marks
(a)
Given that negative 2 plus 3 straight i is a root of the equation f open parentheses x close parentheses equals 0 comma
(i)

show that 2 minus 3 straight i is also a root of f open parentheses x close parentheses equals 0, and 

(ii)

hence find the values of a subscript 1 and a subscript 3in terms of a subscript 5.

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8a
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7 marks

Consider the polynomial function f left parenthesis x right parenthesis equals x to the power of 4 plus a x cubed plus b x squared plus c x plus d,  where a comma space b comma space c comma d space element of straight real numbers. Two distinct roots of f open parentheses x close parentheses equals 0 are given by k plus k squared straight i and k squared plus k straight i,  where k is a real constant. The remainder when f open parentheses x close parentheses is divided by x is 8100.

(a)
(i)
Find the two possible values of k.
 
(ii)
Hence find real values for and  such that left parenthesis x squared plus p x plus q right parenthesis is guaranteed to be a factor of f open parentheses x close parentheses.
8b
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4 marks
(b)
Given that a equals negative 12 , find the values of b and c.

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9a
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4 marks

The polynomial function f is defined by

f left parenthesis x right parenthesis equals 2 a x cubed plus left parenthesis 4 plus 2 a minus a squared right parenthesis x squared minus left parenthesis 6 plus 2 a plus a squared right parenthesis x plus 3 a 

where a not equal to 0 is a real constant. 

The graph of y equals f open parentheses x close parentheses only intersects the x-axis at the point open parentheses a over 2 comma space 0 close parentheses.

(a)
By considering the sum of the roots, use proof by contradiction to show that f open parentheses x close parentheses equals 0 has two non-real roots.
9b
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5 marks
(b)
Find the set of possible values of a.

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