1.已知8x^2y^m与-5x^n+4y^3是同类项,求多项式m^3-3m^2n+3mn^2-n^3的值

由题意知
⑴8x^2y^m与-5x^n+4y^3是同类项,所以
n=2,m=3
m^3-3m^2n+3mn^2-n^3
= 3^3-3×3^4+3×3×2^2-2^3
=27－3×81+3×36-8
=27-243+108-8
=-116
⑵7x³-6x³y+3x³+6x³y-3x²y-10x³
合并同类项后
=-3x²y
若想求-3x²y的值必须知道x,y的值,所以他说的没道理!
⑶ ∵x^m与-4x^2y^n是同类项
∴m=2,n=0
好好学习!