Substitution into Algebraic Expressions

Topic Content:

To substitute means to replace letters in algebraic expressions with values. 

Example 2.3.1:

Find the value of

(a) \( \scriptsize 4x \) 
(b) \( \scriptsize xy \: – \: 5y \) 
(c) \( \scriptsize 5x^2 \: – \: 2y^3 \) 

When x = 2, and y = 3 

Solution 

a. \( \scriptsize 4x \\ = \scriptsize 4 \: \times \: x \\ \scriptsize (x = 2) \\ = \scriptsize 4 \: \times \: 2 = \scriptsize 8\) 

Note: We replaced/substituted x with 2

b. \( \scriptsize xy \: – \: 5y \) 

= \( \scriptsize (x \: \times \: y) \: – \: (5 \: \times \: y) \) 

When x = 2, and y = 3 

Substitute the