Question

（X-Y)^3等于多少?

Answer 1

(X-Y)^3
=(X-Y)(X-Y)(X-Y)
=(X^2-2XY+Y^2)(X-Y)
=X^3-2X^2Y+XY^2-X^2Y+2X^2Y-Y^3
=X^3-3X^2Y+3XY^2-Y^3