Basics & LogarithmshardFree

Basics & Logarithms: Value

JEE Maths question with a full step-by-step solution.

Question
If A=(log31log34)(log39log32)(log31log39)(log38log34)A = \dfrac{(\log_3 1 - \log_3 4)(\log_3 9 - \log_3 2)}{(\log_3 1 - \log_3 9)(\log_3 8 - \log_3 4)}, then the value of 2(3A)2(3^A) is
Solution
Answer: 9
Step 1: Evaluate each logarithm. log31=0\log_3 1 = 0, log34=2log32\log_3 4 = 2\log_3 2, log39=2\log_3 9 = 2, log38=3log32\log_3 8 = 3\log_3 2.
A=(02log32)(2log32)(02)(3log322log32)=2log32log3(9/2)2log32A = \frac{(0 - 2\log_3 2)(2 - \log_3 2)}{(0 - 2)(3\log_3 2 - 2\log_3 2)} = \frac{-2\log_3 2 \cdot \log_3(9/2)}{-2\log_3 2}
Step 2: Simplify (cancelling 2log32-2\log_3 2 from numerator and denominator):
A=log3 ⁣(92)A = \log_3\!\left(\frac{9}{2}\right)
Step 3: Therefore 3A=923^A = \dfrac{9}{2}, and:
2(3A)=292=92(3^A) = 2 \cdot \frac{9}{2} = 9
Answer: 9
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