Metamath Proof Explorer


Theorem subsubd

Description: Law for double subtraction. (Contributed by Mario Carneiro, 27-May-2016)

Ref Expression
Hypotheses negidd.1 ( 𝜑𝐴 ∈ ℂ )
pncand.2 ( 𝜑𝐵 ∈ ℂ )
subaddd.3 ( 𝜑𝐶 ∈ ℂ )
Assertion subsubd ( 𝜑 → ( 𝐴 − ( 𝐵𝐶 ) ) = ( ( 𝐴𝐵 ) + 𝐶 ) )

Proof

Step Hyp Ref Expression
1 negidd.1 ( 𝜑𝐴 ∈ ℂ )
2 pncand.2 ( 𝜑𝐵 ∈ ℂ )
3 subaddd.3 ( 𝜑𝐶 ∈ ℂ )
4 subsub ( ( 𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ ) → ( 𝐴 − ( 𝐵𝐶 ) ) = ( ( 𝐴𝐵 ) + 𝐶 ) )
5 1 2 3 4 syl3anc ( 𝜑 → ( 𝐴 − ( 𝐵𝐶 ) ) = ( ( 𝐴𝐵 ) + 𝐶 ) )