Solve for X : Log (X2 - 21) = 2 - Mathematics

Solve for x : log (x² - 21) = 2.

Sum

log ( x² - 21 ) = 2
⇒ log ( x² - 21) = log 100
⇒ x² - 21 - 100 = 0
⇒ x² - 121 = 0
⇒ x² = 121
⇒ x = `+- sqrt121`
⇒ x =`+-`11

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Laws of Logarithm

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Chapter 8: Logarithms - Exercise 8 (B) [Page 106]

Chapter 8 Logarithms
Exercise 8 (B) | Q 7.2 | Page 106

Express the following in a form free from logarithm:

2 log x - log y = 1

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2 log x + 3 log y = log a

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State, true or false : log 1 x log 1000 = 0