已知-3x^m-2ny^n-2与5分之1x^5y^4-m是同类项,
则：{m-2n=5
n-2=4-m
解得：{m=17/3
n=1/3
∴(m-2n)²-5(m+n)
=[(17/3)-(2/3)]²－5×[(17/3)+(1/3)]
=5²－5×6
=25-30
=-5