Question

已知关于x,y的多项式mx的三次方+3nxy的二次方-2x的三次方-xy的二次方+2x+y中不含三次项，求2m+3m的值

给个具体的答题方案啊

Answer 1

mx^3+3nxy^2-2x^3-xy^2+2x+y
=（m-2)x^3+（3n-1)xy^2+2x+y
不含3次项，则m-2=0，m=2,3n-1=0,n=1/3
2m+3n
=4+1
=5

Answer 2

mx^3+3nxy^2-2x^3-xy^2+2x+y
=（m-2)x^3+（3n-1)xy^2+2x+y
所以，由题意得：不含3次项，则m-2=0，m=2,3n-1=0,n=1/3
2m+3n
=4+1
=5