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Question
Solve the following:
log ( x + 1) + log ( x - 1) = log 11 + 2 log 3
Sum
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Solution
log ( x + 1) + log ( x - 1) = log 11 + 2 log 3
⇒ log [(x + 1)(x - 1)] = log 11 + log 32
⇒ log {x2 - 1} = log (11.9)
⇒ log {x2 - 1} = log99
⇒ x2 - 1 = 99
⇒ x2 = 100
So, x = 10 or -10
Negative value is rejected
So, x = 10.
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