Edexcel 4MA1 • Section 2.2E
Algebraic Proof: The Logic Engine
Master the art of mathematical proof through visual representations and systematic algebraic manipulation
🔬The Proof Engine
Expression: 2n + 1
n = 1, Value = 3
Odd number: One block doesn't pair
💡The Logic Track
📚 The Dictionary
Even number: 2n (has factor of 2)
Odd number: 2n + 1 (even + 1)
Consecutive: n, n+1, n+2
Square number: Write as (...)²
🎯 Proof Strategies
→ Show it's even? Factorise out 2
→ Show it's odd? Get form 2k + 1
→ Show it's a multiple of k? Factorise k
→ Never use x, y, z for consecutive
⚠️ Examiner Traps
❌ DON'T: Write "it's obvious" or "clearly true"
❌ DON'T: Skip algebraic steps
❌ DON'T: Use x, y for consecutive integers
✓ DO: Show every manipulation clearly
✓ DO: End with "therefore..." or "hence..."
Pro Tip: In "Show that..." questions, manipulate the LEFT side until it matches the RIGHT side. Your working IS the proof!
🧮Dynamic Proof Builder
Sum of 3 consecutive integers is divisible by 3
(n) + (n+1) + (n+2)
Let the integers be n, n+1, n+2
n + (n+1) + (n+2)
Expand and collect like terms
3n + 3
Factorise
3(n + 1)
Conclusion: Has factor of 3 ✓
Multiple of 3 PROVEN
Bridge Strategy: Phase 1 (Even/Odd visuals) → Phase 2 (Consecutive patterns) → Phase 3 (Complex algebraic proofs)
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