How do you solve log x + log 3 = log 21logx+log3=log21?

1 Answer
Özgür Özer
Dec 18, 2015

color(white)(xx)=>x=7×⇒x=7

Explanation:

color(white)(xx)logx+log3=log21×logx+log3=log21

The sum of the logarithms is the logarithm of a product of the numbers being added:

color(white)(xx)color(red)(log(3x))=log21×log(3x)=log21
=>color(red)(1/3xx)3x=color(red)(1/3xx)21⇒13×3x=13×21
=>x=7⇒x=7

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