Proof: Manipulation 2

Let's prove the following theorem:

(a ⋅ (b ⋅ (-1))) ⋅ 2 = (a ⋅ b) ⋅ (-2)

Proof:

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Proof Table
# Claim Reason
1 (a ⋅ b) ⋅ (-1) = a ⋅ (b ⋅ (-1)) (a ⋅ b) ⋅ (-1) = a ⋅ (b ⋅ (-1))
2 ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ (b ⋅ (-1))) ⋅ 2 if (a ⋅ b) ⋅ (-1) = a ⋅ (b ⋅ (-1)), then ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ (b ⋅ (-1))) ⋅ 2
3 ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ ((-1) ⋅ 2) ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ ((-1) ⋅ 2)
4 (-1) ⋅ 2 = -2 (-1) ⋅ 2 = -2
5 (a ⋅ b) ⋅ ((-1) ⋅ 2) = (a ⋅ b) ⋅ (-2) if (-1) ⋅ 2 = -2, then (a ⋅ b) ⋅ ((-1) ⋅ 2) = (a ⋅ b) ⋅ (-2)
6 ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ (-2) if (a ⋅ b) ⋅ ((-1) ⋅ 2) = (a ⋅ b) ⋅ (-2) and ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ ((-1) ⋅ 2), then ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ (-2)
7 (a ⋅ (b ⋅ (-1))) ⋅ 2 = (a ⋅ b) ⋅ (-2) if ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ b) ⋅ (-2) and ((a ⋅ b) ⋅ (-1)) ⋅ 2 = (a ⋅ (b ⋅ (-1))) ⋅ 2, then (a ⋅ (b ⋅ (-1))) ⋅ 2 = (a ⋅ b) ⋅ (-2)

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