x²+x-1=0 x²=1-xx²+x-1=0x²+x+1/4=5/4(x+1/2)²=5/4x+1/2=√5/2 或x+1/2=-√5/2x=(√5-1)/2 或 x=(-√5-1)/2 x³+2x+3x³+1+2x+2=(x+1)(x²-x+1)+2(x+1)=(x+1)(x²-x+3) x&...