I need help with this challenging question for my computer discrete structures/data structures class.

Ok I need to prove that the sum of the first n fibonacci numbers is equal to the (n+2)nd fibonacci number minus one using induction.

I don't know how to proceed since I'm stuck at the base case.

Here's my work so far:

P(n): 1+1+2+3+5+8+.........n = (n+2) -1

Base Case: P(1): 1+1+2+3+5+8....+1 = (1+2) -1

1 is not equal to 2 so I'm confused as to why the base case doesn't equal to 1...something wrong.

The question doesn't specify what value to start, but I know P(1) is normally the default case to begin a base case.

Help is greatly appreciated.