# How do you foil (y-4)(y+5)?

Sep 2, 2015

#### Answer:

$\left(y - 4\right) \left(y + 5\right) = \textcolor{b l u e}{{y}^{2} + y - 20}$

#### Explanation:

The expression is : (y−4)(y+5)

F O I L involves carrying out the below operations in the following order:

1) product of First terms :$\left(\textcolor{b l u e}{y \mathmr{and} y}\right)$+

2)product of Outside terms:$\left(\textcolor{b l u e}{y \mathmr{and} 5}\right)$+

3)product of Inside terms:$\left(\textcolor{b l u e}{- 4 \mathmr{and} y}\right)$+

4)product of Last terms:$\left(\textcolor{b l u e}{- 4 \mathmr{and} 5}\right)$

1) $y \cdot y = \textcolor{b l u e}{{y}^{2}} +$

2) $y \cdot 5 = \textcolor{b l u e}{5 y} +$

3) $- 4 \cdot y = \textcolor{b l u e}{- 4 y} +$

4) -4 *5 = color(blue)(-20

adding all the terms

=color(blue)(y^2+5y-4y+(-20)
$= \textcolor{b l u e}{{y}^{2} + y - 20}$