HSC · Mathematics Extension 1 · Proof · also VCE Mathematical Induction live from the app

Proving Summation Formulas Using Induction

Consider proving that 1 plus 2 plus 3 plus dot dot dot plus n equals n times the quantity n plus 1 divided by 2 for all positive integers n. For the base case when n equals 1, the left side equals 1 and the right side equals 1 times 2 divided by 2 which equals 1, confirming the formula holds. Assuming the formula is true for n equals k gives us 1 plus 2 plus dot dot dot plus k equals k times the quantity k plus 1 divided by 2, then adding the next term k plus 1 to both sides yields 1 plus 2 plus dot dot dot plus k plus the quantity k plus 1 equals k times the quantity k plus 1 divided by 2 plus the quantity k plus 1, which simplifies to the quantity k plus 1 times the quantity k plus 2 divided by 2, proving the formula for n equals k plus 1. This is the real knowscape from knowhere, not a picture of one. Drag it. Watch what actually changes.

mathematics extension 1 · proof · proving summation formulas using inductiondrag it · it is yours
the one idea

why this one carries the topic.

Induction never proves the formula outright — it proves that truth is contagious. Show it holds once, then show that whenever it holds it hands itself to the next case, and the whole infinite chain falls for free. You're not summing anything; you're building a machine that sums forever.

Mathematical induction proves summation formulas by first verifying the formula works at n equals 1, then showing if it works for n equals k it must work for n equals k plus 1, establishing truth for all positive integers.

what examiners catch — Examiners check that students correctly expand the sum up to k plus 1 by writing it as the sum up to k plus the new term, not incorrectly treating it as a separate expression.
what you leave with

three things, not forty.

what's underneath

nothing here is a standalone fact.

knowhere maps every concept to what it rests on and what rests on it — 2 underneath this one, 0 built on top. Each one says why, in a sentence, not as an arrow on a diagram.

this conceptproving summation formulas using inductionMathematical induction proves summation formulas by first verifying the formula works at n equals 1, then showing if it works for n equals k it must work for n equals k plus 1, establishing truth for all positive integers.
sits under itthe base casebecause no anchor, no induction
sits under itthe inductive stepbecause the step is the engine of the proof
the rest of proof

5 more, same treatment.

Each one is its own knowscape in the app — built for how a particular student takes things in, not one explanation handed to everybody.

divisibility proofs by inductionin the appthe inductive hypothesisin the appthe inductive stepin the appthe base casein the appdiagnosing a false induction proofin the app
this is one of 865

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knowherehsc mathematics extension 1proving summation formulas using induction