Question

mx -ny=m2+n2,x+y=2m....From linear equations in two variables

Answer 1

m x - n y = m^2 + n^2     and          x + y = 2 m

multiply the second with n and add:

(m+n) x = (m+n)^2
=>   m+n = 0  or          x = m+n
=>  y = 2m - m - n = m  - n