Question:medium

If \(y=e^{4x}(92)^x\); then \(\frac{dy}{dx}\) is equal to
(\(\log_e x=\log x\))

Show Hint

Use the product rule. \(\frac{d}{dx}92^x=92^x\log 92\).
Updated On: Oct 1, 2026
  • \(4x\,e^{4x}\cdot 92^{x-1}\)
  • \(e^{4x}92^{x-1}[368+x]\)
  • \(e^{4x}(92)^x[4+\log 92]\)
  • \(e^{4x}92^x\log 92\)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Use logarithmic differentiation.
Take the natural log of \(y=e^{4x}92^x\). Products turn into sums, which are easier to handle.
\[ \ln y=4x+x\ln 92 \]

Step 2: Differentiate both sides.
On the left, \(\frac{d}{dx}\ln y=\frac{1}{y}\frac{dy}{dx}\). On the right, \(\ln 92\) is a constant, so the right side gives \(4+\ln 92\).
\[ \frac{1}{y}\frac{dy}{dx}=4+\ln 92 \]

Step 3: Multiply back by y.
\[ \frac{dy}{dx}=y\,(4+\ln 92)=e^{4x}(92)^x\,(4+\ln 92) \]

Step 4: Match with the options.
The question says \(\log_e x=\log x\), so \(\ln 92=\log 92\) here. The result equals option 3. The other options have a factor like \(x\) or \(92^{x-1}\), which only appear when the exponent is wrongly treated as a fixed power.

Final Answer:
So \(\frac{dy}{dx}=e^{4x}(92)^x[4+\log 92]\). \[ \boxed{e^{4x}(92)^x\,[4+\log 92]} \]
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