# What is the vertex form of y=(x + 7)(x + 3) ?

Oct 17, 2016

The vertex form is $y = {\left(x + 5\right)}^{2} - 4$

#### Explanation:

$y = \left(x + 7\right) \left(x + 3\right) = {x}^{2} + 10 x + 21 = {x}^{2} + 10 x + 25 - 4$
$y = {\left(x + 5\right)}^{2} - 4$
The vertex is at $x = - 5$ which is also a line of symmetry
and the vertex is at $\left(- 5 , - 4\right)$

graph{x^2+10x+21 [-10, 10, -5, 5]}