x²-x-2=0 x²-8x+12=0 x²+2=3x x²+4x=21

问题描述:

x²-x-2=0 x²-8x+12=0 x²+2=3x x²+4x=21

x²-x-2=0(x+1)(x-2)=0x=2 或x= -1x²-8x+12=0(x-2)(x-6)=0x=2或 x=6x²+2=3xx²-3x+2=0(x-1)(x-2)=0x=1或x=2x²+4x=21x²+4x-21=0(x+7)(x-3)=0x=3或x=-7