(x²+3x+3)(x²+3x-4)=8(x²+3x)²-(x²+3x)-12-8=0(x²+3x)²-(x²+3x)-20=0(x²+3x-5)(x²+3x+4)=0x²+3x-5=0x=（-3±√29）/2或x²+3x+4=0Δ=9-16=-7