Limits, Continuity and Differentiability
80286
If \(y=\log \left[a^{3 x}\left(\frac{5-x}{x+4}\right)^{\frac{3}{4}}\right]\), then \(\frac{d y}{d x}=\)
1 \(3+\frac{3}{4(5-x)}-\frac{3}{4(x+4)}\)
2 \(\frac{3}{\log a}-\frac{3}{4(5-x)}-\frac{3}{(4 x+4)}\)
3 \(\frac{3}{\mathrm{a}}+\frac{3}{4(5-\mathrm{x})}-\frac{3}{4(\mathrm{x}+4)}\)
4 \(3 \log a-\frac{3}{4(5-x)}-\frac{3}{4(x+4)}\)
Explanation:
(D) : Given,
\(y=\log \left[a^{3 x}\left(\frac{5-x}{x+4}\right)^{3 / 4}\right]\)
We know that,
\(\log (m . n)=\log m+\log n\)
\(\log \mathrm{a}^{\mathrm{n}}=\mathrm{n} \log \mathrm{a}\)
\(\log \frac{a}{b}=\log a-\log b\)
Then,
\(y =\log a^{3 x}+\log \left(\frac{5-x}{x+4}\right)^{3 / 4}\)
\(y =3 x \log a+\frac{3}{4} \log \left(\frac{5-x}{x+4}\right)\)
\(y =3(\log a) x+\frac{3}{4}[\log (5-x)-\log (x+4)]\)
\(\therefore \quad \frac{d y}{d x} =3 \log a+\frac{3}{4}\left[\frac{-1}{5-x}-\frac{1}{x+4}\right]\)
\(\frac{d y}{d x} =3 \log a-\frac{3}{4(5-x)}-\frac{3}{4(x+4)}\)