Functions (Edexcel GCSE Maths: Higher)

Exam Questions

2 hours32 questions
1a
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1 mark

straight f and straight g are functions such that

               straight f open parentheses x close parentheses space equals space 2 over x squared space space space space space space space space space space and space space space space space space straight g open parentheses x close parentheses space equals space 4 x cubed

Find straight f left parenthesis negative 5 right parenthesis

1b
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2 marks

Find fg open parentheses 1 close parentheses

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2a
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2 marks

      straight f open parentheses x close parentheses space equals space 3 x space minus space 2
straight g open parentheses x close parentheses space equals fraction numerator space 10 over denominator x plus 2 end fraction

Express the inverse function straight f to the power of negative 1 end exponent in the form straight f to the power of negative 1 end exponent open parentheses x close parentheses space equals space...

2b
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2 marks

Find gf left parenthesis x right parenthesis
Simplify your answer.

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3a
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1 mark

f is a function such that

straight f open parentheses x close parentheses space equals space fraction numerator 1 over denominator x squared space plus space 1 end fraction

Find straight f open parentheses begin inline style 1 half end style close parentheses

3b
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2 marks

straight g is a function such that

straight g open parentheses x close parentheses space equals space square root of x minus 1 end root comma space space x greater-than or slanted equal to 1

Find straight f g open parentheses x close parentheses

Give your answer as simply as possible.

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4a
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1 mark

straight f spaceis the function straight f left parenthesis x right parenthesis space equals space 2 x space plus space 5

Find straight f left parenthesis 3 right parenthesis

4b
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2 marks

Express the inverse function straight f to the power of negative 1 end exponent in the form straight f to the power of negative 1 end exponent open parentheses x close parentheses =

4c
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1 mark

straight g is the function straight g left parenthesis x right parenthesis space equals space x squared space long dash space 25

Find straight g left parenthesis long dash 3 right parenthesis

4d
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5 marks

i) Find gf left parenthesis x right parenthesis
Give your answer as simply as possible.

[3]

ii) Solve gf left parenthesis x right parenthesis space equals space 0

[2]

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5a
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1 mark

The functions straight f and straight g are defined as

straight f open parentheses x close parentheses space equals space 1 half x space plus 4
straight g open parentheses x close parentheses space equals space fraction numerator 2 x over denominator x plus 1 end fraction

Work out straight f left parenthesis 6 right parenthesis

5b
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2 marks

Work out  fg left parenthesis long dash 3 right parenthesis

5c
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2 marks

straight g left parenthesis a right parenthesis space equals space minus 2

Work out the value of a.

5d
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3 marks

Express the inverse function straight f to the power of negative 1 end exponent in the form straight f to the power of negative 1 end exponent left parenthesis x right parenthesis = ...

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6a
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1 mark

f is the function such that  f(x) = 2x - 5
g is the function such that g(x) = x2 - 10

Find f (4)

6b
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2 marks

Find fg(-4)

6c
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2 marks

Express the inverse function f-1 in the form f-1 (x) = ...

6d
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4 marks

Solve gf (x) = -1

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7a
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1 mark

The functions straight f and straight g are such that

 space straight f left parenthesis x right parenthesis space equals space 3 left parenthesis x long dash space 4 right parenthesis space and space straight g left parenthesis x right parenthesis space equals x over 5 plus 1

Find the value of straight f open parentheses 10 close parentheses

7b
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2 marks

Find  straight g to the power of negative 1 end exponent open parentheses x close parentheses

7c
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2 marks

Show that ff left parenthesis x right parenthesis space equals space 9 x space long dash space 48

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8
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1 mark

straight g open parentheses x close parentheses equals 2 x and  straight h open parentheses x close parentheses equals fraction numerator x minus 1 over denominator 2 end fraction

Circle the expression for hg left parenthesis x right parenthesis

fraction numerator 2 x squared minus x over denominator 2 end fraction

fraction numerator 2 x minus 1 over denominator 2 end fraction

x squared minus x

x minus 1

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9
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1 mark

straight f left parenthesis x right parenthesis space equals space 3 x

Circle the expression forspace straight f to the power of negative 1 end exponent left parenthesis x right parenthesis

negative 3 x

3 over x

fraction numerator 1 over denominator 3 x end fraction

x over 3

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10a
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2 marks

A function is represented by the following function machine.

q8a-paper4-spec2015-ocr-gcse-maths

A number is input into the machine.
The output is used as a new input.
The second output is 11.

Work out the number that was the first input.

10b
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3 marks

A number is input into the machine.
The output given is the same number.

Work out the number.

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1
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3 marks

straight f left parenthesis x right parenthesis space equals space 3 x squared long dash 2 x long dash 8

Express space straight f left parenthesis x space plus space 2 right parenthesis space in the form a x squared space plus space b x

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2a
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3 marks

The functions straight f and straight g are such that straight f left parenthesis x right parenthesis space equals space x space plus space 3     and       straight g open parentheses x close parentheses space equals space fraction numerator 1 over denominator x minus 2 end fraction

Find space fg left parenthesis x right parenthesis space
Give your answer as a single algebraic fraction expressed as simply as possible.

2b
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3 marks

Express the inverse function straight g to the power of negative 1 end exponent in the form straight g to the power of negative 1 end exponent open parentheses x close parentheses space equals space...

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3a
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2 marks

The function straight f is such that

straight f left parenthesis x right parenthesis space equals space 4 x long dash space 1

Find straight f to the power of negative 1 end exponent left parenthesis x right parenthesis

3b
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2 marks

The function straight g is such that

straight g left parenthesis x right parenthesis space equals space k x squared where k is a constant.

Given that fg left parenthesis 2 right parenthesis space equals space 12

work out the value of k

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4a
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2 marks

The functions straight f and straight g are such that

straight f open parentheses x close parentheses space equals space 3 x space minus 1 space space space space and space space space space space space space straight g open parentheses x close parentheses space equals space x squared plus 4

Find straight f to the power of negative 1 end exponent left parenthesis x right parenthesis

4b
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5 marks

Given that fg left parenthesis x right parenthesis space equals space 2 gf left parenthesis x right parenthesis,

show that 15 x to the power of 2 space end exponent minus space 12 x long dash 1 equals space 0

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5
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4 marks

straight f open parentheses x close parentheses equals 2 x minus 3 and straight g open parentheses x close parentheses equals x squared

Show that  straight f to the power of negative 1 end exponent open parentheses 55 close parentheses equals straight f g open parentheses 4 close parentheses

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6
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2 marks

straight f left parenthesis x right parenthesis space equals space x over 3 plus space 4  for all values of x.

straight g left parenthesis x right parenthesis space equals space 6 x squared space plus space 3 for all values of x.

Work out fg left parenthesis x right parenthesis.

Give your answer in the form a x squared space plus space b   where a and b are integers.

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7
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3 marks

table row cell straight f open parentheses x close parentheses end cell equals cell c x plus d end cell row cell straight f open parentheses 4 close parentheses end cell equals 7 row cell straight f open parentheses 10 close parentheses end cell equals 22 end table

Work out the values of c and d.

c space equals.........................     

d space equals.........................     

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8
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2 marks

straight f left parenthesis x right parenthesis space equals space 3 x squared space – space 4 x space plus space 8 for all values of x

Jenny says,

“f(10) must equal 2 × f(5), because 10 is 2 × 5”

Is Jenny correct?
Show working to support your answer.

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9
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3 marks

straight g left parenthesis x right parenthesis space equals space 16 space – space x space space space space straight h left parenthesis x right parenthesis space equals space x cubed

Solve    gh open parentheses x close parentheses equals 24

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10
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3 marks

straight f left parenthesis x right parenthesis space equals space fraction numerator x over denominator x plus 2 end fraction space space space space space space space space space space space space space space space space space straight g left parenthesis x right parenthesis space equals space x squared space – space 2

Work out fg left parenthesis x right parenthesis

Give your answer in the form    a space plus space b x to the power of n    where a comma space b and n are integers.

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11
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4 marks

space straight f left parenthesis x right parenthesis space equals space fraction numerator 2 x space plus space 3 over denominator x minus 4 end fraction

Work out straight f to the power of – 1 end exponent space left parenthesis x right parenthesis

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12
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3 marks

straight g open parentheses x close parentheses space equals space 3 x plus 7

Solve  straight g to the power of – 1 end exponent space left parenthesis x right parenthesis space equals space 2 x

x = ....................

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13
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3 marks

A function machine is shown below.

q8b-paper4-spec2015-ocr-gcse-maths

If the Input is 3, the Output is 5.
If the Input is 7, the Output is 25.

Use this information to fill in the two boxes.

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1a
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2 marks

Show that fraction numerator x squared space plus space 3 x over denominator 2 x squared space plus space 5 x minus 3 end fraction can be written as  fraction numerator x over denominator k x space minus 1 end fraction

State the value of k.

1b
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3 marks

straight f left parenthesis x right parenthesis space equals space fraction numerator x over denominator 2 x space minus 1 end fraction

Find the inverse function straight f space to the power of negative 1 end exponent  in the form straight f space to the power of negative 1 end exponent open parentheses x close parentheses space equals space.......
Show your working clearly.

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2
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5 marks

The functions straight f and straight g are such that

straight f left parenthesis x right parenthesis space equals space 5 x space plus space 3 space space space space straight g left parenthesis x right parenthesis space equals space a x space plus space b where a and b are constants.

straight g left parenthesis 3 right parenthesis space equals 20 space space space space space space space and space space space space space space straight f to the power of negative 1 end exponent left parenthesis 33 right parenthesis equals space straight g left parenthesis 1 right parenthesis

Find the value of a and the value of b.

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3
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4 marks

straight f open parentheses x close parentheses equals 1 half x      straight g open parentheses x close parentheses equals x minus x squared

Solve  straight f to the power of – 1 end exponent left parenthesis x right parenthesis space equals space gf left parenthesis x right parenthesis

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4
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5 marks

straight f open parentheses x close parentheses equals fraction numerator 2 x over denominator 5 end fraction minus 1

Work out the value of  straight f to the power of – 1 end exponent left parenthesis 3 right parenthesis space plus space straight f left parenthesis – 0.5 right parenthesis

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5
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3 marks

straight f open parentheses x close parentheses space equals space 5 minus x  and     straight g open parentheses x close parentheses space equals space 3 x plus 7

Simplify straight f left parenthesis 2 x right parenthesis space plus space straight g left parenthesis x space – space 1 right parenthesis

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6
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2 marks

straight h left parenthesis x right parenthesis space equals space cube root of x   for all values of x

On the grid, draw the graph of the inverse function y equals straight h to the power of negative 1 end exponent open parentheses x close parentheses  for  negative 2 less-than or slanted equal to x less-than or slanted equal to 2

q27a-paper2h-june2017-aqa-gcse-maths

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7
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2 marks

For all values of x

straight f left parenthesis x right parenthesis space equals space sin space x
straight g left parenthesis x right parenthesis space equals space x space plus space 90

On the grid, draw the graph of the composite function  y equals fg open parentheses x close parentheses  for  0 degree space less-than or slanted equal to space x space less-than or slanted equal to space 360 degree

q27b-paper2h-june2017-aqa-gcse-maths

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8
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3 marks

straight f left parenthesis x right parenthesis space equals space 2 x space plus space c

straight g left parenthesis x right parenthesis space equals space c x space plus space 5

straight f g left parenthesis x right parenthesis space equals space 6 x space plus space d

c and d are constants.

Work out the value of d space.

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9
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4 marks

Here are two function machines, A and B.

q19-paper3h-specimen2015-aqa-gcse-maths

Both machines have the same input.

Work out the range of input values for which

                                   the output of A is less than the output of B.

 

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