17) The answer is (D)

Indeed, we have $f(2)-\frac{2 f(1)+1}{2}$, that is $2=\frac{2 f(1)+1}{2}$, from which $4=2 f(1)+1$ and finally $f(1)=\frac{3}{2}$.
17) Given a function such that $f(x+1)=\frac{2 f(x)+1}{2}$ and such that $f(2)=2$, what is the value of $f(1)$?
(A) 0
(B) $1 / 2$
(C) 1
(D) $3 / 2$
(E) 2.