原式=(x-y)^(3×6)×[-(x-y)]³×[3(x-y)]²=-9(x-y)^(18+3+2)=-9(x-y)^23
原式=(x-y)^(3×6)×[-(x-y)]³×3(x-y)²=-3(x-y)^(18+3+2]=-3(x-y)^23 （就是-3(x-y)的23次方）
原式=(x-y)^(3×6)×[-(x-y)]³×2(x-y)²=-2(x-y)^(18+3+2]=-2(x-y)^23
