# How do you factor 4a^2 + 20a + 25?

Jun 26, 2015

It is a perfect square trinomial:
$4 {a}^{2} + 20 a + 25 = {\left(2 a + 5\right)}^{2}$

#### Explanation:

The first term is the square of $2 a$

The last term is the square of $5$

Multiplt those two, then doubles the number. Is that the middle term? If yes, then it is a perfect square.

$2 a \times 5 = 10 a$. Now double that (multiply by $2$): $2 \times 10 a = 20 a$ Yes, that is the middle term on the original expression, so it is a perfect square,