(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简

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(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简

(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简
(m+n)!/(m+n-2)!-n!/(n-2)!=62怎么化简

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

=(m+n)(m+n-1)-n(n-1)=m*m+2mn-m=62