# How do you factor 25x^2-9?

Jul 26, 2015

You write the expression as a difference of two perfect squares.

#### Explanation:

You can factor your expression by writing it as a difference of two perfect squares, for which you know that

${a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$

In your case, you can write

$25 {x}^{2} - 9 = 5 x \cdot 5 x - 3 \cdot 3$, which is equivalent to

${\left(5 x\right)}^{2} - {3}^{2} = \textcolor{g r e e n}{\left(5 x - 3\right) \left(5 x + 3\right)}$