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Solve the Following: Log ( X + 1) + Log ( X - 1) = Log 11 + 2 Log 3 - Mathematics

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Question

Solve the following:
log ( x + 1) + log ( x - 1) = log 11 + 2 log 3

Sum

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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More About Logarithm
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Chapter 10: Logarithms - Exercise 10.2

APPEARS IN

Frank Mathematics [English] Class 9 ICSE
Chapter 10 Logarithms
Exercise 10.2 | Q 7.4
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