Question

已知M=2xy/x^2-y^2,N=x^2+y^2/x^2-y^2,

Answer 1

x:y=5:2

所以y=2x/5

M+N

=2xy/(x^2-y^2)+(x^2+y^2)/(x^2-y^2)

=(x^2+2xy+y^2)/(x^2-y^2)

=(x+y)^2/(x+y)(x-y)

=(x+y)/(x-y)

=(x+2x/5)/(x-2x/5)

=(7x/5)/(3x/5)

=7/3