Algebra

a^2 - 18, when a = 6

Step-by-step solution with explanation

Final Answer

Step-by-step solution

1

Write the expression with given value

We are given the expression and told that a equals 6. Our job is to substitute 6 in place of a and simplify.
2

Substitute 6 in for a

Replace every a in the expression with 6. Using parentheses keeps things clear and avoids sign errors.
3

Evaluate the exponent first

6 squared means 6 times 6, which equals 36. Order of operations (PEMDAS) tells us to handle exponents before subtraction.
4

Subtract to get the final value

36 minus 18 equals 18. This is our final answer.

Understanding this problem

Learning Insight

Substitution works because a variable is just a placeholder for a number. Once you swap in the number, the expression becomes a straightforward arithmetic problem. The order of operations (PEMDAS) then guides exactly how to simplify it.

Quick Tip

Always put the substituted number in parentheses — like (6)^2 instead of 6^2 written loosely — so you square the whole value and avoid accidental sign mistakes.

Common Mistake

A common mistake is computing 6^2 as 6 × 2 = 12 instead of 6 × 6 = 36. Remember, an exponent means repeated multiplication, not regular multiplication by the exponent.