(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成 m(m+2n-1)=62 求详解

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(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成m(m+2n-1)=62求详解(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成m(m+2n-1)=62求详解(m+n

(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成 m(m+2n-1)=62 求详解
(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成 m(m+2n-1)=62 求详解

(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简成 m(m+2n-1)=62 求详解
(m+n)!/(m+n-2)!-n!/(n-2)!
=(m+n)(m+n-1)(m+n-2)!/(m+n-2)!-n(n-1)(n-2)!/(n-2)!
=(m+n)(m+n-1)-n(n-1)
=m^2+mn-m+mn+n^2-n-n^2+n
=m^2+2mn-m
= m(m+2n-1)