Lesson 1: Evaluating Algebraic Expressions

Objectives

At the end of this lesson, students should be able to:

• Substitute numbers for words and letters in formulae.
• Evaluate algebraic expressions when the value for each variable is given.

We use numbers in place of letters and symbols to calculate the actual value of an algebraic expression. This might require the use of BODMAS.

Brackets

Order (squares, cubes, etc.)

Division

Multiplication

Addition

Subtraction

Example 1

Given that x = 2, y = 3 and  z = 5, find the values of the following expressions:

1. 2x – z
2. 3y + x²
3. 8(x + y)

Solution

1. 2x – z = 2 (2) – 5

=    4 – 5

=     – 1

2. 3y + x² = 3(3) + (2)²

=   9 + 4

=   13

3. 8(x + y) = 8 (2 + 3)

= 8 (5)

= 40