多项式3x^2y-xy+2y^2与2x^2y+2xy-y^2的和与差把结果抽x的升幂排列:和:差.求

问题描述:

多项式3x^2y-xy+2y^2与2x^2y+2xy-y^2的和与差把结果抽x的升幂排列:和:差.求

和:
3x^2y-xy+2y^2+2x^2y+2xy-y^2
=y²+xy+5x²y
差:
3x^2y-xy+2y^2-(2x^2y+2xy-y^2)
=3x^2y-xy+2y^2-2x^2y-2xy+y^2
=3y²-3xy+x²y