proofs Flashcards by disgruntled snail

Prove that -a(-b) = ab

-a(-b)
= -a(-b) + 0
= -a(-b) + a(0)
= -a(-b) + a(-b + b)
= -a(-b) + a(-b) + a(b)
= -b(-a + a) + a(b)
= -b(0) + a(b)
= 0 + a(b)
= ab

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