MAT 108: Introduction to Abstract Mathematics
Hint for Question 4
For (a), I used induction.
The first part of (b) should follow pretty quickly from (a).
Finding the limit of the sequence requires writing down an explicit formula for x_n: you should prove first that x_n = (2^n - 1)/(2^(n-1)). (If this were on an exam, I would give you this formula.)
Then, identify and prove the limit using the epsilon-N definition of the limit.