Can u ! i am not sure how to do this

Write an explicit formula that represents the sequence defined by the following recursive formula:

Use the function nest to evaluate p(x) = 1 + x + · · · + x50 at x = 1.00001. (use the matlab ones command to save typing.) find the error of the computation by comparing with the equivalent expression q(x) = (x51 − 1)/(x − 1).

What is the y intercept of f(x)=(1/2)^x?