If a, b, c are in continued proportion, prove that :(i) (a + b)/(b + c) = [a^2(b − c)] / [b^2(a − b)] (ii) (a + b + c)/(a − b + c) = (a + b + c)^2 / (a^2 + b^2 + c^2) (iii) (a^2 + ab + b^2)/(b^2 + bc + c^2) = a/c (iv) (a + b + c)(a − b + c) = (a^2 + b^2 + c^2) (v) a^2 b^2 c^2 (a^−3 + b^−3 + c^−3) = (a^3 + b^3 + c^3)