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 Description: Law for addition and subtraction. (Contributed by NM, 19-Aug-2001.) (Proof shortened by Andrew Salmon, 22-Oct-2011.)
Assertion
Ref Expression
addsub ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐴 + 𝐵) − 𝐶) = ((𝐴𝐶) + 𝐵))

StepHypRef Expression
1 addcom 10540 . . . 4 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (𝐴 + 𝐵) = (𝐵 + 𝐴))
21oveq1d 6919 . . 3 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐴 + 𝐵) − 𝐶) = ((𝐵 + 𝐴) − 𝐶))
323adant3 1168 . 2 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐴 + 𝐵) − 𝐶) = ((𝐵 + 𝐴) − 𝐶))
4 addsubass 10611 . . 3 ((𝐵 ∈ ℂ ∧ 𝐴 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐵 + 𝐴) − 𝐶) = (𝐵 + (𝐴𝐶)))
543com12 1159 . 2 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐵 + 𝐴) − 𝐶) = (𝐵 + (𝐴𝐶)))
6 subcl 10599 . . . . 5 ((𝐴 ∈ ℂ ∧ 𝐶 ∈ ℂ) → (𝐴𝐶) ∈ ℂ)
7 addcom 10540 . . . . 5 ((𝐵 ∈ ℂ ∧ (𝐴𝐶) ∈ ℂ) → (𝐵 + (𝐴𝐶)) = ((𝐴𝐶) + 𝐵))
86, 7sylan2 588 . . . 4 ((𝐵 ∈ ℂ ∧ (𝐴 ∈ ℂ ∧ 𝐶 ∈ ℂ)) → (𝐵 + (𝐴𝐶)) = ((𝐴𝐶) + 𝐵))
983impb 1149 . . 3 ((𝐵 ∈ ℂ ∧ 𝐴 ∈ ℂ ∧ 𝐶 ∈ ℂ) → (𝐵 + (𝐴𝐶)) = ((𝐴𝐶) + 𝐵))
1093com12 1159 . 2 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → (𝐵 + (𝐴𝐶)) = ((𝐴𝐶) + 𝐵))
113, 5, 103eqtrd 2864 1 ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → ((𝐴 + 𝐵) − 𝐶) = ((𝐴𝐶) + 𝐵))