.
then f(2) = f(1 + 1) = f(1) + f(1) = 17 + 17 = 34. ANSWER
f(3) = f(1 + 2) = f(1) + f(2) = 17 + 34 = 51. ANSWER
f(4) = f(2 + 2) = f(2) + f(2) = and you continue from this point.
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For the last question, the answer is "NO".
As an counterexample, consider f(x) = x^2.
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