Page 102 Chapter two exercise:

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.

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