Year 7: Symbolic substitution in algebraic expressions

What is Symbolic Substitution?

Symbolic substitution is a really useful trick in algebra. It means replacing a letter (a variable) in an algebraic expression with a specific number. This helps you simplify expressions, evaluate them for different values, and even solve equations.

How to Do It

1. Identify the Variable: First, find the letter in the expression that represents a missing number.
2. Choose a Value: Pick a number to replace the variable with.
3. Substitute: Replace every instance of the variable in the expression with the chosen number.
4. Simplify (if possible): After substitution, simplify the new expression using your regular algebraic rules.

Examples

Example 1: For the expression 2x + 3, if x = 2, then 2(2) + 3 = 4 + 3 = 7

Example 2: For the expression 5y - 8, if y = -1, then 5(-1) - 8 = -5 - 8 = -13

Why Do We Do It?

Symbolic substitution helps you:

• Evaluate expressions
• Solve equations
• Understand how changes in variables affect the expression's value