Respostas

2014-06-29T22:09:11-03:00
(b+a)²=b²+2ab+b²
nesse caso
b=2x a=-4

(2x)²+2*2x*(-4)+(-4)²=0
4x²-16x+16=0
simplificando (/4)
x²-4x+4=0
delta=(-4)²-4*1*4=0

x=(-(-4)±√0)/2
x=2
2014-06-29T22:13:23-03:00