Step by step
The question
Question: factor x² − 25.
Factor means: write it as a times, with brackets.
x2 − 25
1 Two squares
This is one square take away another square.
x² is x squared.
25 is 5 squared.
A square minus a square is the plus bracket times the minus bracket.
a² − b² = (a + b)(a − b)
x2 = (x)²
25 = 5²
So we get (x + 5)(x − 5).
= (x + 5)(x − 5)
2 Check
Let's check: we multiply it back out.
Each part of the first bracket times each part of the second.
Check: (x + 5)(x − 5) = x2 − 5x + 5x − 25
= x2 − 25
We get x² − 25 again.
So (x + 5)(x − 5) is right!
Let's look back.
First: two squares.
Last: check.
Answer
= (x + 5)(x − 5)