# How do you write #f(x)=4*(x-3)(x+7)# into standard form?

##### 1 Answer

Feb 3, 2017

#### Explanation:

You can use the FOIL mnemonic to enumerate all of the combinations you need to add together if you find it helpful:

#f(x) = 4*(x-3)(x+7)#

#color(white)(f(x)) = 4(overbrace((x)(x))^"First"+overbrace((x)(7))^"Outside"+overbrace((-3)(x))^"Inside"+overbrace((-3)(7))^"Last")#

#color(white)(f(x)) = 4(x^2+7x-3x-21)#

#color(white)(f(x)) = 4(x^2+4x-21)#

#color(white)(f(x)) = 4x^2+16x-84#