# What is the standard form of  y= (x + 9)(x – 1) ?

Nov 29, 2015

$y = {x}^{2} + 8 x - 9$

#### Explanation:

$y = x \left(x - 1\right) + 9 \left(x - 1\right)$ It is distributive!

$y = \textcolor{b r o w n}{\left(x \times x\right)} + \textcolor{b l u e}{\left(x \times \left\{- 1\right\}\right)} + \textcolor{red}{\left(9 \times x\right)} + \textcolor{g r e e n}{\left(9 \times \left\{- 1\right\}\right)}$

$y = \textcolor{b r o w n}{{x}^{2}} \textcolor{b l u e}{- x} \textcolor{red}{+ 9 x} \textcolor{g r e e n}{- 9}$

$y = {x}^{2} + 8 x - 9$