Question

If a: b=c: d, prove that
a^2+c^2/ab+cd =ab+cd /b^2+d^2

Answer 1

Answer:

(a+b)2(c+d)2=abcd and (a−b)2(c−d)2=abcd.

So

a+bc+d=a−bc−d⇒ac=a−bc−d and bd=a−bc−d

and the result follows.