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Mathematics

Show that log3 9 + log3 3 = log5 125

Logarithms

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Answer

Given: log3 9 + log3 3 = log5 125

Taking L.H.S:

= log3 9 + log3 3

= log 93\dfrac{9}{3} + log 33\dfrac{3}{3}

= log 323\dfrac{3^2}{3} + log 33\dfrac{3}{3}

= 2log 33\dfrac{3}{3} + log 33\dfrac{3}{3}

= 2 x 1 + 1

= 2 + 1

= 3

Taking R.H.S.:

= log5 125

= log 1255\dfrac{125}{5}

= log 535\dfrac{5^3}{5}

= 3log 55\dfrac{5}{5}

= 3 x 1

= 3

Thus, L.H.S. = R.H.S.

Hence, log3 9 + log3 3 = log5 125.

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