Question

已知关于x、y的多项式mx^3+3nxy^2-2x^3-xy^2+2x+y中不含三次项,求2m+3n的值

Answer 1

mx^3+3nxy^2-2x^3-xy^2+2x+y

=x^3(m-2)+xy^2(3n-1)+2x+y

m-2=0

3n-1=0

m=2

n=1/3

2m+3n

=4+1

=5