exam oriented an important question from ML aggarwal, class 10th, chapter 7, ratio and proportion, Avichal publication

It is given that x/a = y/b = z/c

Then prove that

(i)x³/a²+ y³/b²+z³/c²=(x+y+z)³/(a+b+c)²

(ii) [a²x²+b²y²+c²z²/a³x+b³y+c³z] ³=xyz/abc

(iii)(ax-by) /(a+b)(x-y) +(by-cz) /(b+c)(y-z) +(cz-ax) /(c+a) (z-x) =3

Question no. 16, exercise 7. 2