1)mn^2/n^2-m^2*(2/m-2/n)2)(u/u-v-u/u+v)*u^2+uv/2v3)(a+b)^2:(1/a^2+1/b^2+2/ab)

1) mn/n - m(2/m-2/n) = mn/n - (m 2)/m + (2 m)/n = mmn/mn - 2mn/
/mn + 2nmm/mn = (mmn - 2mn + 2nmm)/mn = (mn - 2mn + 2mn)/mn
= (2mn - mn)/mn = mn(2m - m)/mn = (2m - m)/n
2) (u/u - v - u/u + v) u + uv/2v = uu/u - vu/1 - uu/u + vu/1 + uv/2v = uu2v/u2v- - u2vvu/u2v - uu2v/u2v + vuu2v/u2v + uuv/u2v = (uu2v - u2vvu - uu2v +
+ vuu2v + uuv)/2uv = (2uv - 2uv - 2uv + 2uv + uv)/2uv = uv/2uv = u/2
3) (a + b) (1/a + 1/b + 2/ab) = (a + b)(a + b)/1 (b/ab + a/ab + 2ab/ab) =
= (a + b)(a + b)/1 (a + 2ab + b)/ad = (a + b)(a + b)/1 (a + b)(a + b)/ad = (a + b)(a + b)/1 ad/(a + b)(a + b) = (a + b)(a + b)ad/(a + b)(a + b) = ad