# What is the vertex form of y=(x – 8)(x + 5) ?

Jul 10, 2017

Vertex form is $y = {\left(x - \frac{3}{2}\right)}^{2} - \frac{169}{4}$

#### Explanation:

Start by multiplying out.

$y = {x}^{2} - 3 x - 40$

Now complete the square.

$y = 1 \left({x}^{2} - 3 x + \frac{9}{4} - \frac{9}{4}\right) - 40$

$y = 1 \left({x}^{2} - 3 x + \frac{9}{4}\right) - \frac{9}{4} - 40$

$y = 1 {\left(x - \frac{3}{2}\right)}^{2} - \frac{169}{4}$

Hopefully this helps!