Question

已知-5x^2m-1yⁿ与11xⁿ⁺²y^-4-3m的积与x⁷y是同类项，试求出2n-m-9的值．

Answer 1

-5x^2m-1yⁿ•11xⁿ⁺²y^-4-3m
=-55x^2m-1+n+2y^n-4-3m
∵与x⁷y是同类项，
∴由同类项的定义，得

2m-1+n+2=7 n-4-3m=1

解得：

m= 1 5 n= 28 5

．
∴2n-m-9
=2×

28

5

-

1

5

-9
=2．