Algebra

a^2 - 8 when a = 4

Step-by-step solution with explanation

Final Answer

Step-by-step solution

1

Write the expression with the variable

This is the expression we need to evaluate. We are given a specific value for 'a', so we will substitute it in.
2

Substitute a = 4 into the expression

Replace every 'a' with 4. Using parentheses keeps things clear and avoids mistakes.
3

Calculate the exponent first

Order of operations says exponents come before subtraction. .
4

Subtract to get the final value

Simple subtraction gives us our answer. The expression equals 8 when a = 4.

Understanding this problem

Learning Insight

Evaluating an expression means swapping the variable for a number and then following order of operations (PEMDAS). The exponent must be handled before subtraction — that's why the order of steps matters, not just the arithmetic.

Quick Tip

Always put the substituted number in parentheses — writing instead of helps you remember to square the whole value, especially when negatives are involved.

Common Mistake

A common mistake is computing as (multiplying by 2) instead of (squaring). For example, writing instead of .