计算（x-y)³-1 27（x-3)³-8y³
问题描述：
计算（x-y)³-1 27（x-3)³-8y³
计算（x-y)³-1
27（x-3)³-8y³
答
a^3-b^3=（a-b）*（a^2+ab+b^2）
（x-y)^3-1
=(x-y-1)[(x-y)^2+x+y+1]
=(x-y-1)[(x^2-2xy+y^2+x+y+1]
27（x-3)^3-8y^3
=3^3*（x-3)^3-2^3*y^3
=(3x-9-2y)[9(x-3)^2+3(x-3)*2y+4y^2]
=(3x-2y-9)[9x^2-54x+81+6xy-18y+4y^2]