(3-y)²=2y(y-3)
=(3-y)²-2y(y-3)
=(3-y)²+2y(3-y)
=(3-y)(3-y+2y)
=(3-y)(3+y)3x²-(x+2)²+2x=0两题都是公式法，谢谢，还有这题我还以为是化简..(3-y)²=2y(y-3)9-6y+y²=2y²-6y整理得y²=9，此题不用公式法的∴y1=3，y2=-3 3x²-(x+2)²+2x=0整理得2x²-2x+4=0运用公式x=[-b±(√b²-4ac)]/2a解得x1=-1，x2=2