x²-(x-2y)(x+2y)+(x²-y)(y+x²)=?
问题描述:
x²-(x-2y)(x+2y)+(x²-y)(y+x²)=?
答
x²-(x²-4y²)+(x^4-y²)
=4y²+x^4-y²
=x^4-3y².