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iGCSE (2021 Edition)

5.03 Polynomial theorems

Worksheet
Polynomial division
1

Simplify the following:

a

\dfrac{\left( n^{7} r^{2}\right)^{4}}{\left( n^{4} r\right)^{4}}

b

\dfrac{9 x^{5} + 8 x^{4}}{x}

c

\dfrac{40 x^{3} - 48 x^{2} + 32}{8}

d

\dfrac{15 x^{4} - 24 x^{3} - 21 x^{2} + 12 x}{3 x}

2

Complete the following statement:

\dfrac{⬚ x^{7} - ⬚ x^{5}}{2 x^{⬚}} = 3 x^{4} - 4 x^{2}

3

What polynomial, when divided by 2 x^{2}, produces 8 x^{6} - 5 x^{4} + 6 x^{2} as a quotient?

Remainder theorem
4

For each of the following, find the remainder when P \left( x \right) is divided by A \left( x \right):

a

P \left( x \right) = 3 x^{4} - 3 x^{3} - 5 x^{2} + 4 x - 5, A \left( x \right) = x + 5

b

P \left( x \right) = 3 x^{4} + 5 x^{3} - 2 x^{2} + 6 x + 7, A \left( x \right) = 3 x + 1

c

P \left( x \right) = 2x^4-3x^3+6x^2-10, A \left( x \right) = x -1

d

P \left( x \right) = x^3-2x^2+9x-1, A \left( x \right) = x-4

e

P \left( x \right) = 4x^5-6x^3-7x^2+9x, A \left( x \right) = 2x-5

f

P \left( x \right) = 6x^4-x^3+9x^2+10x-8, A \left( x \right) = 4x+2

5

Find the value of k for each of the following:

a

The remainder when 3 x^{3} + 4 x^{2} + 4 x + k is divided by x - 2 is 52.

b

The remainder when 4 x^{3} - 2 x^{2} + k x-1 is divided by x - 2 is 15.

6

Write down all the possible rational zeros of the following polynomials:

a

P \left( x \right) = 3 x^{4} - 3 x^{3} - 2 x^{2} + 5 x + 6

b

P \left( x \right) = 6 x^{4} + 9 x^{3} + 2 x^{2} + 5 x + 4

c

P \left( x \right) = x^{3} + 4 x^{2} - 7 x - 10

7

Is \dfrac{2}{5} a possible rational zero of P \left( x \right) = 5 x^{3} - 4 x^{2} - 7 x + 10?

8

The polynomials P \left( x \right) = x^{3} + 2 x^{2} - 5 x + n and Q \left( x \right) = x^{3} + 4 x - 11 give the same remainder when divided by x - 4. Solve for n.

9

Consider the polynomials P \left( x \right) = x^{4} - 5 x^{3} - k x + m and Q \left( x \right) = k x^{2} + m x - 5. The remainder when P \left( x \right) is divided by x + 2 is 53, while the remainder when Q \left( x \right) is divided by x + 2 is - 31.

a

Solve for k.

b

Solve for m.

c

Hence, find the remainder when P \left( x \right) is divided by x - 4.

Factor theorem
10

Write the following polynomials as a product of linear factors:

a

x^{3} - 6 x^{2} + 11 x - 6

b

4 x^{3} - x^{2} - 29 x + 30

11

Consider the polynomial P \left( x \right) = x^{3} - 4 x^{2} - 11 x + 30.

a

Write down all the possible zeros.

b

Find the value of P \left( - 1 \right).

c

Find the value of P \left( - 3 \right).

d

Find the value of P \left( 2 \right).

e

Factorise P \left( x \right) = x^{3} - 4 x^{2} - 11 x + 30.

12

Consider the division \dfrac{4 x^{2} - 3 x - 6}{x - 2}.

a

Find the remainder.

b

Is x - 2 a factor of P \left( x \right)?

13

Consider the division \dfrac{x^{3} - 5 x^{2} - 2 x - 1}{x + 1}.

a

Find the remainder.

b

Is x + 1 a factor of P \left( x \right) ?

14

Consider the division \dfrac{x^{2} + 4 x - 32}{x + 8}.

a

Find the remainder.

b

Is x + 8 a factor of P \left( x \right)?

c

Factorise x^{2} + 4 x - 32.

15

Show that x + 2 is a factor of P \left( x \right) = x^{4} + 7 x^{3} + 8 x^{2} - 28 x - 48.

16

Consider \left( 4 x^{3} + 20 x^{2} + 3 x + 15\right) \div \left(x + 5\right).

a

Show that x + 5 is a factor of P \left( x \right).

b

Factorise 4 x^{3} + 20 x^{2} + 3 x + 15.

17

Consider \left(12 + 9 x + x^{2} - x^{3}\right) \div \left(4 - x\right).

a

Show that 4 - x is a factor of P \left( x \right).

b

Factorise 12 + 9 x + x^{2} - x^{3}.

18

The polynomial P \left( x \right) = x^{3} + a x^{2} + b - 10 x is divisible by both x+1 and x+2.

a

Solve for the value of a.

b

Hence, solve for the value of b.

19

The polynomials 4 x^{2} - 13 x - 12 and 5 x^{2} + 11 x + k have a common factor of x + p, where p is an integer.

a

Solve for p.

b

Hence, solve for k.

20

The polynomial 3 x^{3} + p x^{2} + q x + 2 has a factor of x + 1, but when divided by x - 1, it leaves a remainder of 24.

a

Solve for p.

b

Solve for q.

c

Hence, factorise the polynomial completely.

21

The polynomial P \left( x \right) = x^{3} + a x^{2} + b + 40 x is divisible by both x+3 and x+4.

a

Solve for a.

b

Hence, solve for b.

22

The polynomial 3 x^{3} + p x^{2} + 8 x + q is divisible by x^{2} - 7 x + 12.

a

Solve for p.

b

Solve for q.

c

Hence, factorise the cubic completely.

23

The polynomial Q \left( x \right) = x^{4} + 8 x^{3} + a x^{2} - 74 x + b is divisible by both x - 3 and x + 5.

a

Solve for a.

b

Solve for b.

c

Hence, factorise Q \left( x \right) completely.

Applications
24

Consider the rectangle shown with an area of (2 x^{4} - 8 x)\text{ units}^2:

Find a polynomial expression for its length.

25

Consider the rectangle shown with an area of (21 x^{3} + 6 x^{2} - 15 x - 9)\text{ units}^2:

Find a polynomial expression for its length.

26

Consider the triangle shown with the given area of (19 n^{3} + 13 n^{2} + 11 n)\text{ units}^2.

Find a polynomial expression for its height.

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Outcomes

0606C5.1

Know and use the remainder and factor theorems.

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