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Question Number 32500 by 7991 last updated on 26/Mar/18
proof: (−a)(−b)=ab
proof:(−a)(−b)=ab
Answered by Joel578 last updated on 26/Mar/18
We know (−1).(−1) = 1 and (−1) . a = −a, a ∈ R (−a)(−b) = [(−1) . a][(−1) . b] = [(−1)(−1)] [a . b] = 1 . ab = ab
Weknow(−1).(−1)=1and(−1).a=−a,a∈R(−a)(−b)=[(−1).a][(−1).b]=[(−1)(−1)][a.b]=1.ab=ab

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