x²+2x-3=0
x²+2x+1-1-3=0
(x+1)²-4=0
(x+1+2)(x+1-2)=0
(x+3)(x-1)=0
x=3或x=-1
x²-7x+6=0
x²-7x+49/4-49/4+6=0
(x-7/2)^2-25/4=0
(x-7/2-5/2)(x-7/2+5/2)=0
(x-6)(x-1)=0
x=6或x=1
x²+2x-1=0
x²+2x+1-1-1=0
(x+1)^2-2=0
(x+1-√2)(x+1+√2)=0
x=-1+√2或x=-1-√2