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MHT CET · Maths · Differentiation

If \(\mathrm{f}(x)=3^x ; \mathrm{g}(x)=4^x\), then \(\frac{\mathrm{f}^{\prime}(0)-\mathrm{g}^{\prime}(0)}{1+\mathrm{f}^{\prime}(0) \mathrm{g}^{\prime}(0)}\) is

  1. A \(\frac{\log \left(\frac{3}{4}\right)}{1+(\log 3)(\log 4)}\)
  2. B \(\frac{\log \left(\frac{3}{4}\right)}{1+\log 12}\)
  3. C \(\frac{\log 12}{1+\log 12}\)
  4. D \(\frac{\log \left(\frac{3}{4}\right)}{1-\log 12}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{\log \left(\frac{3}{4}\right)}{1+(\log 3)(\log 4)}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{f}^{\prime}(x)=3^x \log 3 \Rightarrow \mathrm{f}^{\prime}(0)=\log 3 \)
\( \mathrm{~g}^{\prime}(x)=4^x \log 4 \Rightarrow \mathrm{g}^{\prime}(0)=\log 4 \)
\( \therefore \frac{\mathrm{f}^{\prime}(0)-\mathrm{g}^{\prime}(0)}{1+\mathrm{f}^{\prime}(0) \mathrm{g}^{\prime}(0)} =\frac{\log 3-\log 4}{1+(\log 3)(\log 4)} \)
\( =\frac{\log \left(\frac{3}{4}\right)}{1+(\log 3)(\log 4)}\)