(1)x^2+2x-3=0
x^2+2x+1=3+1
(x+1)^2=4
x+1=±2
x1=1,x2=-3
(2)x^2-2x-8=0
x^2-2x+1=8+1
(x-1)^2=9
x-1=±3
x1=4,x2=-2