I'm sorry but the question is in the attachment because I seem to have a problem uploading equations in fractions. If you refer to the question, I'm not sure whether the 'above recurrence relation' refers to the one in V_{n}or f(V_{n}), but assuming it's the one in f(V_{n}), I tried comparing the gradients of the tangent [f'(V_{n}) = f(V_{n})/ (V_{n}- V_{n+1})] but I don't know how to proceed from there.

Please help me and sorry for the inconvenience caused!