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1 vote

If a - b = - 7 and a2 + b2 = 85, then find ab.

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If a - b = - 7 and a2 + b2 = 85, then find ab.


1). 18
2). -30
3). -44
4). -60


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1 answers

2 vote
Answered by on | Votes 2 |

(a - b)2 = a2 + b2 - 2ab

Given, a - b = - 7 and a2 + b2 = 85

⇒ 49 = 85 - 2ab

⇒ 2ab = 36

⇒ ab = 18 

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