Year 8: Symbolic substitution in algebraic expressions

What is symbolic substitution?

Symbolic substitution is a way of replacing variables in algebraic expressions with specific numbers or other values. This allows you to simplify expressions, evaluate them for particular values, or even solve equations.

Steps for symbolic substitution

1. Identify the variable: Find the variable in the expression (e.g., 'x', 'y', 'a').
2. Substitute the value: Replace the variable with the given number or expression.
3. Simplify (if possible): After substitution, simplify the resulting expression using your knowledge of order of operations.

Examples

Example 1: Evaluate $2x+3$ when $x=5$

Substitute x with 5: $2\left(5\right)+3=10+3=13$

Example 2: Evaluate $3y^2-2y$ when $y=-2$

Substitute y with -2: $3{(-2)}^2-2(-2)=3\left(4\right)+4=12+4=16$

Important notes

Remember to follow the order of operations (BODMAS/PEMDAS) after substituting. Carefully substitute the correct value into the expression. Double-check your calculations.