Page 102 Chapter two exercise:

See the example here.

Key point to prove that "if S(k) is true then S(k+1) is true." :
    Sum of the 1st term  to the (k+1)^th term = Sum of the 1st term to the k^th term + the (k+1)^th term.
    Replace the answer of Sum of the 1st term to the k^th term to the last step and simplify it.

Click here for more practice.