我想問x^3-y^3的公式是......

x³士y³=(x士y)(x²干xy+y²)
proof:
R.H.S.
=(x士y)(x²干xy+y²)
=x³干x²y+xy²士x²y-xy²士y³
=x³干x²y士x²y+xy²-xy²士y³
=x³士y³
The proof is completed.

(x-y)(x+y)(x-y)

x^3-y^3= (x-y)(x^2+xy+y^2)
x^3+y^3=(x+y)(x^2-xy+y^2)