Polynomial Functions (DP IB Analysis & Approaches (AA): HL): Exam Questions

4 hours32 questions
1a2 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.

Polynomial functions Medium Q1

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.  

Find the value of k.

2a2 marks

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.

2b2 marks

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

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.

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.

4a
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4 marks

Factorise fully 6 x cubed plus x squared minus 12 x plus 5.

4b7 marks

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.

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.

Show that 2 is a root of g left parenthesis x right parenthesis.

5b
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5 marks

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.

65 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.

7a5 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. 

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

Hence find a and b.

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.

9a
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5 marks

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

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.

104 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.

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. 

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

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

11c
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4 marks

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

12a2 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. 

Find alpha plus beta and alpha beta, in terms of k.

12b2 marks

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

Hence find the value of k .

13a2 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

Find the value of k.

13b
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3 marks

Fully factorise f left parenthesis x right parenthesis.

13c
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3 marks

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.

1a4 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.

Find the values of p and q.

1b
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3 marks

Find the roots of f open parentheses x close parentheses.

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.

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

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.

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.

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

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.

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

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.

54 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.

66 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.

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.

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.

9a2 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.

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

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.

10a6 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.

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.

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.

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.

Show that p equals 8  and find the value of q.

1b
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6 marks

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.  .

2a2 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

Explain why n must be even.

2b4 marks

Given that n is as small as possible, find an equation for f open parentheses x close parentheses.

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.

Sketch the graph of y equals f open parentheses x close parentheses. Label the coordinates where the graph crosses the coordinate axes.

3b1 mark

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.

Find a and b in terms of m and n.

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.

 

57 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. .

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

Find the value of k.

6b2 marks

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

Find the values of p and q.

7a2 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

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

7b6 marks

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.

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 space 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.

(i) Find the two possible values of k.  

(ii) Hence find real values for p and q 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.

8b4 marks

Given that a equals negative 12 , find the values of b and c.

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.

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

Find the set of possible values of a.