factoring
what 2 numbers multiply to get -12 and add to get -4?
-6 and 2
(x-6)(x+2)=0
set to zero
x-6=0
x=6
x+2=0
x=-2
x=-2 and 6
complete the square
isolate x terms
(x^2-4x)-12=0
take 1/2 of -4 and square it ((-2)^2=4)
now add positive and neagtive inside
(x^2-4x+4-4)-12=0
factor perfect square
((x-2)^2-4)-12=0
get rid of parenthasees
(x-2)^2-4-12=0
(x-2)^2-16=0
add 16 both sides
(x-2)^2=16
sqrt both sides, don't forget positive an dneagit ve roots
x-2=+/-4
add 2 to both sides
x=2+/-4
x=2+4=6
x=2-4=-2
x=-2 and 6
