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## JSS1: MATHEMATICS - 2ND TERM

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#### Quizzes

Lesson 2, Topic 4
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# Substitution into an Algebraic Expression

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Substitution into an algebraic expression is the process of replacing a letter with a number, in a given algebraic expression. The letters are called variables because they can be replaced by any value.

### Example

If  x =  2  and y  =  3

Find the following:

i. $$\scriptsize x \: + \: 6$$
ii. $$\scriptsize 4 \: + \: x \: + \: y$$
iii. $$\scriptsize y \: – \: x$$
iv. $$\scriptsize 10 \: – \: 2y \: – \: 3$$

Solution

i. $$\scriptsize x + 6 \\ = \scriptsize 2 + 6 = \scriptsize 8$$

ii. $$\scriptsize 4 + x + y \\ = \scriptsize 4 + 2 + 3 = \scriptsize 9$$

iii. $$\scriptsize y \: – \: x \\ = \scriptsize 3 \: – \: 2 = \scriptsize 1$$

iv. $$\scriptsize 10 \: – \: 2y \: – \: 3 \\ = \scriptsize 10 \: – \: 2(3) \: – \: 3 \\ = \scriptsize 10 \: – \: 6 \: – \: 3 = \scriptsize 1$$