Solving Equations with Complex Roots (Edexcel International A Level (IAL) Further Maths: Further Pure 1): Exam Questions

Exam code: YFM01

2 hours12 questions
1a
1 mark

straight f left parenthesis z right parenthesis equals z to the power of 4 plus 6 z cubed plus 76 z squared plus a z plus b

where a and b are real constants.

Given that negative 3 plus 8 straight i is a complex root of the equation straight f left parenthesis z right parenthesis space equals space 0

write down another complex root of this equation.

1b
6 marks

Hence, or otherwise, find the other roots of the equation straight f left parenthesis z right parenthesis space equals space 0

1c
2 marks

Show on a single Argand diagram all four roots of the equation straight f left parenthesis z right parenthesis space equals space 0

2a
Sme Calculator
2 marks

In this question you must show all stages of your working.

Solutions relying entirely on calculator technology are not acceptable.

straight f left parenthesis z right parenthesis equals z cubed minus 13 z squared plus 59 z plus p      p element of straight integer numbers

Given that z equals 3 is a root of the equation straight f left parenthesis z right parenthesis space equals space 0

show that p equals negative 87

2b
Sme Calculator
4 marks

Use algebra to determine the other roots of straight f left parenthesis z right parenthesis space equals space 0 , giving your answers in simplest form.

2c
1 mark

On an Argand diagram

  • the root z equals 3 is represented by the point P

  • the other roots of straight f left parenthesis z right parenthesis equals 0 are represented by the points Q and R

  • the number z equals negative 9 is represented by the point S

Show on a single Argand diagram the positions of P, Q , R and S

2d
2 marks

Determine the perimeter of the quadrilateral P Q S R, giving your answer as a simplified surd.

3a
1 mark

straight f left parenthesis z right parenthesis equals 2 z cubed plus p z squared plus q z minus 41

where p and q are integers.

The complex number 5 minus 4 straight i is a root of the equation straight f left parenthesis straight z right parenthesis space equals space 0

Write down another complex root of this equation.

3b
4 marks

Solve the equation straight f left parenthesis straight z right parenthesis space equals space 0 completely.

3c
2 marks

Determine the value of p and the value of q.

3d
2 marks

When plotted on an Argand diagram, the points representing the roots of the equation straight f left parenthesis z right parenthesis space equals space 0 form the vertices of a triangle.

Determine the area of this triangle.

4a
1 mark

straight f left parenthesis z right parenthesis equals 2 z cubed plus p z squared plus q z minus 41

where p and q are integers.

The complex number 5 minus 4 straight i is a root of the equation straight f left parenthesis straight z right parenthesis space equals space 0

Write down another complex root of this equation.

4b
4 marks

Solve the equation straight f left parenthesis straight z right parenthesis space equals space 0 completely.

4c
2 marks

Determine the value of p and the value of q.

4d
2 marks

When plotted on an Argand diagram, the points representing the roots of the equation straight f left parenthesis z right parenthesis space equals space 0 form the vertices of a triangle.

Determine the area of this triangle.

5a
1 mark

In this question you must show all stages of your working.
Solutions relying on calculator technology are not acceptable.

Given that x equals 2 plus 3 i is a root of the equation

2 x to the power of 4 minus 8 x cubed plus 29 x squared minus 12 x plus 39 equals 0

Write down another complex root of this equation.

5b
4 marks

Use algebra to determine the other 2 roots of the equation.

5c
1 mark

Show all 4 roots on a single Argand diagram.

6a
2 marks

In this question you must show all stages of your working.

Solutions relying entirely on calculator technology are not acceptable.

straight f left parenthesis z right parenthesis equals 4 z cubed plus p z squared minus 24 z plus 108

where p is a constant.

Given that negative 3 is a root of the equation straight f left parenthesis z right parenthesis equals 0

determine the value of p

6b
4 marks

using algebra, solve straight f left parenthesis z right parenthesis equals 0 completely, giving the roots in simplest form,

6c
2 marks

determine the modulus of the complex roots of straight f left parenthesis z right parenthesis equals 0

6d
2 marks

show the roots of straight f left parenthesis z right parenthesis equals 0 on a single Argand diagram.

7a
1 mark

straight f left parenthesis z right parenthesis equals 2 z to the power of 4 minus 19 z cubed plus A z squared plus B z minus 156

where Aand Bare constants.

The complex number 5 minus straight i is a root of the equation straight f left parenthesis z right parenthesis equals 0

Write down another complex root of this equation.

7b
5 marks

Solve the equation straight f left parenthesis z right parenthesis equals 0 completely.

7c
2 marks

Determine the value of A and the value of B.

8a
1 mark

The equation

x to the power of 4 plus A x cubed plus B x squared plus C x plus 225 equals 0

where A comma space B and C are real constants, has

  • a complex root 4 space plus space 3 i

  • a repeated positive real root

Write down the other complex root of this equation.

8b
2 marks

Hence determine a quadratic factor of x to the power of 4 plus A x cubed plus B x squared plus C x plus 225

8c
2 marks

Deduce the real root of the equation.

8d
3 marks

Hence determine the value of each of the constants A, B and C

9a
1 mark

f left parenthesis z right parenthesis space equals space 2 z cubed space space – space z squared space space plus space a z space plus space b

where a and b are integers.

The complex number negative 1 space minus space 3 i is a root of the equation f left parenthesis z right parenthesis space equals space 0

Write down another complex root of this equation.

9b
4 marks

Determine the value of a and the value of b.

9c
2 marks

Show all the roots of the equation f left parenthesis z right parenthesis space equals space 0 on a single Argand diagram.

10a
3 marks

f left parenthesis x right parenthesis equals left parenthesis 9 x squared plus d right parenthesis left parenthesis x squared minus 8 x plus left parenthesis 10 d plus 1 right parenthesis right parenthesis

where d is a positive constant.

Find the four roots of f left parenthesis x right parenthesis giving your answers in terms of d.

10b
2 marks

Given d space equals space 4, express these four roots in the form a space plus space i b, where a comma b element of straight real numbers

10c
2 marks

Show these four roots on a single Argand diagram.

11a
2 marks

Given that x equals 3 over 8 plus fraction numerator square root of 71 over denominator 8 end fraction   i is a root of the equation

4 x cubed minus 19 x squared plus p x plus q equals 0

Write down the other complex root of the equation.

11b
4 marks

Given that x space equals space 4 is also a root of the equation,

find the value of p and the value of q.

12a
2 marks

straight f left parenthesis z right parenthesis equals z to the power of 4 plus a z cubed plus b z squared plus c z plus d

where a, b, c and d are integers.

The complex numbers 3 plus straight i and negative 1 minus 2 straight i are roots of the equation straight f left parenthesis z right parenthesis space equals space 0

Write down the other roots of this equation.

12b
2 marks

Show all the roots of the equation straight f left parenthesis z right parenthesis space equals space 0 on a single Argand diagram.

12c
5 marks

Determine the values of a, b, c and d.