Designate by (Un) te sequence defined by : U1=2
2Un+1=Un+1
Let (Vn) be the sequence defined by Vn=Un +a
calculate a so that the sequence (Vn) is goemetric .
1. Go back and reread the problem. What you have written is impossible.
2. Try! What do you know about geometric series? What are the first three or four values of $\displaystyle U_n$: $\displaystyle U_2$, $\displaystyle U_3$, $\displaystyle U_4$? Can you guess the general formula for $\displaystyle U_n$?