-4x的5m次方y的3m-n次方÷(-2x的m+2n次方y的2m+n次方)的商与-1/2x的3次方y的2次方是同类项,求

∵-4x^(5m)y^(3m-n)÷[-2x^(m+2n)y^(2m+n)]
=(-4)/(-2)*x^(5m)/x^(m+2n)* y^(3m-n)/y^(2m+n)
=2x^(5m-m-2n)y^(3m-n-2m-n)
=2x^(4m-2n)y^(m-2n)
又-4x^(5m)y^(3m-n)÷[-2x^(m+2n)y^(2m+n)] 的商与-1/2x^3y^2次方是同类项
∴4m-2n=3,且m-2n=2
解得m=1/3,n=-5/6
∴m+n=-1/2