Question 33428
The zero Product Rule :
If ab = 0, then a = 0 or b = 0.   
{{{x^2}}}+4x = -4
{{{x^2}}}+4x+4 = 0
{{{x^2}}}+2x+2x+4 = 0
x(x+2)+2(x+2)=0
(x+2)(x+2)=0
so according to Zero - Product principle
(x+2) = 0 or (x+2) = 0
x+2-2 = 0 -2
x = -2