Mathematical induction — Base case and inductive expansion

Question

For the statement " is divisible by ", write the base case value and expand under the hypothesis .

This practice question was inspired by Question 12(d) in the 2024 NSW HSC Mathematics Extension 1 examination, © NESA. It is an original TestMum variation that practises the same mathematical idea, not an official NESA question.

Set up the solution: show the base case, state the assumption for n=k, and transform the k+1 case using that assumption.Base value: .
Finish the calculation, then check that the result meets the question’s conditions.Expansion: .
State the final answer clearly in the form the question requested.Answer: base ; inductive form , hence divisible by .

Common mistake: changing so many features that the new example no longer tests the same mathematical idea.

Verification: Both checkpoints appear in the NESA marking guidelines.

Any mark labels are a TestMum study aid, not an official NESA marking allocation.