x^2+5x+6=3x^2+2
2x^2-5x-4=0
(2x+1)(x-4)=0
x1=-1/2,x2=4==那（x+1）^2-(x-1)(1-x)=6x^2+2x+1-(-x^2+2x-1)=62x^2+2=6x^2=2x=±√2