Question

要使代数式mx立方;+3nxy平方;+2x立方;-xy平方;+y不含三次项,则2m+3n=

Answer 1

mx³+3nxy²+2x³-xy²+y

=(m+2)x³+(3n-1)xy²+y

其中x³和xy²项数均为三次,要多项式不含三次项,只有

m+2=0 m=-2

3n-1=0 n=1/3

2m+3n=2(-2)+3(1/3)=-4+1=-3