x²-(x-2y)(x+2y)+(x²-y)(y+x²)=?

问题描述:

x²-(x-2y)(x+2y)+(x²-y)(y+x²)=?

x²-(x²-4y²)+(x^4-y²)
=4y²+x^4-y²
=x^4-3y².