Question

化简求值2(x^2+3y^3-xy^2)-2(x^2y+2y^3)+3(x^3-xy^2+x^2y),其中x=-3,y=2

Answer 1

合并同类项
2(x^2+3y^3-xy^2)-2(x^2y+2y^3)+3(x^3-xy^2+x^2y)
=2x^2+6y^3-2xy^2-2x^2y-4y^3+3x^3-3xy^2+3x^2y
=3x^3+2x^2+x^2y-5xy^2+2y^3
带入x=-3 y=2
得3x^3+2x^2+x^2y-5xy^2+2y^3
=3x(-3)^3+2x(-3)^2+(-3)^2x2-5x(-3)x2^2+2x2^3
=-81+18+18+60+16=31

追问

sorry，题打错了
2(x^2y+3y^3-xy^2)-2(x^2y+2y^3)+3(x^3-xy^2+x^2y),其中x=-3,y=2

追答

。。。吃晚饭给你啊

追问

额……我也在吃饭。。

追答

2(x^2y+3y^3-xy^2)-2(x^2y+2y^3)+3(x^3-xy^2+x^2y)
=2x^2y+6y^3-2xy^2-2x^2y-4y^3+3x^3-3xy^2+3x^2y

=3x^3+3x^2y-5xy^2+2y^3
带入x=-3 y=2
3x^3+3x^2y-5xy^2+2y^3
=3x(-3)^3+3x(-3)^2x2-5x(-3)x2^2+2x2^3
=-81+54+60+16
=49