(mn-m²)÷(m²-2mn+n²)/mn·(m²-n²)/m²

问题描述:

(mn-m²)÷(m²-2mn+n²)/mn·(m²-n²)/m²

(mn-m²)÷(m²-2mn+n²)/mn·(m²-n²)/m²
=m(n-m) · (mn)/(m-n)² · (m+n)(m-n)/m²
=-n(m+n)