# What is the standard form of y=(x-1)(x+4) ?

##### 1 Answer
Jan 6, 2016

$y = {x}^{2} + 3 x - 4$

#### Explanation:

You can use FOIL to help multiply this out:

$\left(x - 1\right) \left(x + 4\right)$

$= \stackrel{\text{First" overbrace(x*x) + stackrel "Outside" overbrace(x*4) + stackrel "Inside" overbrace(-1*x) + stackrel "Last}}{\overbrace{- 1 \cdot 4}}$

$= {x}^{2} + 4 x - x - 4$

$= {x}^{2} + 3 x - 4$