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

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