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NSWMaths Extension 1Proof (ME-P1)

Quick questions on Mathematical induction for inequalities: the technique and the algebraic care

3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is the four-part structure?
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The structure is the same template as every induction, adapted to an inequality E(n)F(n)E(n) \le F(n) (or strict, or reversed) for all nn0n \ge n_0:
What is the use-then-strengthen two-step (the core technique)?
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The technique that makes inductive steps for inequalities work is a two-step chain: use the hypothesis to bound the k+1k + 1 expression, then strengthen that bound until it reaches the target. Concretely, to prove LHS(k+1)>RHS(k+1)\text{LHS}(k + 1) > \text{RHS}(k + 1):
What is direction errors when multiplying?
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Multiplying both sides by a quantity preserves the inequality only if the quantity is positive; a negative multiplier flips it.

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