Question

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

Answer 1

`(y-4)(y+5) = color(blue)(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 :`(color(blue)(y and y))`+

2)product of Outside terms:`(color(blue)(y and 5))`+

3)product of Inside terms:`(color(blue)(-4 and y))`+

4)product of Last terms:`(color(blue)(-4 and 5))`

1) `y*y=color(blue)(y^2) +`

2) `y* 5=color(blue)(5y)+`

3) `-4 * y = color(blue)(-4y)+`

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

adding all the terms

`=color(blue)(y^2+5y-4y+(-20)`
`=color(blue)(y^2+y-20)`