Algebra 1 / Chapter 2: Multiplication / Reordering Theorems
Proof: Swap Terms 2 and 3
Let's prove the following theorem:
(a ⋅ b) ⋅ c = (a ⋅ c) ⋅ b
Proof:
| # | Claim | Reason |
|---|---|---|
| 1 | (a ⋅ b) ⋅ c = a ⋅ (b ⋅ c) | (a ⋅ b) ⋅ c = a ⋅ (b ⋅ c) |
| 2 | b ⋅ c = c ⋅ b | b ⋅ c = c ⋅ b |
| 3 | a ⋅ (b ⋅ c) = a ⋅ (c ⋅ b) | if b ⋅ c = c ⋅ b, then a ⋅ (b ⋅ c) = a ⋅ (c ⋅ b) |
| 4 | a ⋅ (c ⋅ b) = (a ⋅ c) ⋅ b | a ⋅ (c ⋅ b) = (a ⋅ c) ⋅ b |
| 5 | (a ⋅ b) ⋅ c = (a ⋅ c) ⋅ b | if a ⋅ (c ⋅ b) = (a ⋅ c) ⋅ b and a ⋅ (b ⋅ c) = a ⋅ (c ⋅ b) and (a ⋅ b) ⋅ c = a ⋅ (b ⋅ c), then (a ⋅ b) ⋅ c = (a ⋅ c) ⋅ b |
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