原式=(x^2-8x+16)^3(x+1)^6/(x^2-2x+1)^3(x-4)^4(x+2)^2
=(x-4)^6(x+1)^6 / (x-1)^6(x-4)^4(x+2)^2
=(x-4)^2(x+1)^6 / (x-1)^6(x+2)^2