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  1. Maths
  2. Year 8
  3. Algebra: Expressions
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Substituting Negative Numbers

In this worksheet, students substitute negative numbers into algebraic expressions.

'Substituting Negative Numbers' worksheet

Key stage:  KS 3

Curriculum topic:   Algebra

Curriculum subtopic:   Understand Expressions, Equations, Inequalities, Terms and Factors

Difficulty level:  

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Worksheet Overview

QUESTION 1 of 10

In this worksheet, we will learn how to substitute negative numbers.

 

Substitute the negative numbers into the expressions instead of the letter.


Example

Evaluate
2x+3
4x
   when X = -5  

leaving your answer as a fraction.    

 

Answer

2x(-5)+3
4x(-5)
=
-10+3
-20
=
-7
-20
=
7
20
 


 

Remember: Multiplying or dividing two negative numbers gives a positive answer.

Multiplying or dividing one positive and one negative number, gives a negative answer.

Work out the following:

 

3x + 4
5x
   =  _______

 

when x = -5

(Leave your answer as a fraction such as 3/4)

 

Work out the following:

5x2 = _________  when x = -3

Work out the value of:

7x2 = _________  when x = -1

Work out the value of:

4x2 - 2 = _________  when x = -5

Work out the value of:

(7x)2 = _________  when x = -2

Work out:

8x2 = _________  when x = -1

Work out:

7(x - 1)2 = _________  when x = -2

Work out the following:

 

2x + 2
3x
   =  _______

 

when x = -4

(Leave your answer as a fraction such as 3/4)

Work out the value of:

(6x)2 = _________  when x = -2

Work out the value of:

6x2 = _________  when x = -2

  • ANSWERS
  • Question 1

Work out the following:

 

3x + 4
5x
   =  _______

 

when x = -5

(Leave your answer as a fraction such as 3/4)

 

CORRECT ANSWER
11/25
EDDIE SAYS
3x + 4
5x
=
3(-5) + 4
5(-5)
=
-15 + 4
-25
=
11
25

 

  • ANSWERS
  • Question 2

Work out the following:

5x2 = _________  when x = -3

CORRECT ANSWER
45
EDDIE SAYS
Remember to work out the power first 5 (-3)2 5 x 9 45
  • ANSWERS
  • Question 3

Work out the value of:

7x2 = _________  when x = -1

CORRECT ANSWER
7
EDDIE SAYS
Remember to work out the power first 7 (-1)2 7 x 1 7
  • ANSWERS
  • Question 4

Work out the value of:

4x2 - 2 = _________  when x = -5

CORRECT ANSWER
98
EDDIE SAYS
Remember to work out the power first 4 (-5)2 - 2 4 x 25 - 2 98
  • ANSWERS
  • Question 5

Work out the value of:

(7x)2 = _________  when x = -2

CORRECT ANSWER
196
EDDIE SAYS
Remember to work out the brackets first (7 x -2)2 (-14)2 196
  • ANSWERS
  • Question 6

Work out:

8x2 = _________  when x = -1

CORRECT ANSWER
8
EDDIE SAYS
Remember to work out the power first 8 (-1)2 - 2 8x 1 8
  • ANSWERS
  • Question 7

Work out:

7(x - 1)2 = _________  when x = -2

CORRECT ANSWER
63
EDDIE SAYS
Remember to work out the bracket first, then the power. Remember to work out the power first 7(-2 -1)2 7 x (-3)2 7 x 9 63
  • ANSWERS
  • Question 8

Work out the following:

 

2x + 2
3x
   =  _______

 

when x = -4

(Leave your answer as a fraction such as 3/4)

CORRECT ANSWER
1/2
EDDIE SAYS
2x + 2
3x
=
2(-4) + 2
3(-4)
=
-8 + 2
-12
=
1
2

 

  • ANSWERS
  • Question 9

Work out the value of:

(6x)2 = _________  when x = -2

CORRECT ANSWER
144
EDDIE SAYS
Remember to work out the brackets first (6 x -2)2 (-12)2 144
  • ANSWERS
  • Question 10

Work out the value of:

6x2 = _________  when x = -2

CORRECT ANSWER
24
EDDIE SAYS
Remember to work out the power first 6 (-2)2 6 x 4 24
---- OR ----

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