Question

要使多项式2mx³+3nxy²+5x³-xy²+y不含三次项,求2m+3n的值

Answer 1

2mx^3+3nxy^2+5x^3-xy^2+y

=(2m+5)x^3+(3n-1)xy^2+y不含3次项

2m+5=0,3n-1=0

2m=-5,3n=1

2m+3n=-5+1=-4