Question

已知m(m-1)-(m^2-n)=3 求m^2+n^2/2-mn 的值

要具体过程，谢谢

Answer 1

m(m-1)-(m^2-n)=3
即 -m + n=3
(-m + n)^2 = m^2-2mn+n^2=9
(m^2+n^2)/2-mn = 9/2

Answer 2

m(m-1)-(m^2-n)=3
m²-m-m²+n=3
-m+n=3
m-n=-3

(m^2+n^2)/2-mn
=(m²-2mn+n²)/2
=(m-n)²/2
=9/2