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QJEEM24Mac71a: JEE Main 2024 Mathematics - Class 12 JEEM24Mac71a Solution: Let be a function satisfying for all . If , then

Let f:R−{0}→Rf: \mathbb{R}-\{0\} \rightarrow \mathbb{R} be a function satisfying f(xy)=f(x)f(y)f\left(\frac{x}{y}\right)=\frac{f(x)}{f(y)} for all x,y,f(y)≠0x, y, f(y) \neq 0 . If f′(1)=2024f^{\prime}(1)=2024 , then

Multiple Choice Options

  • A xf′(x)+2024f(x)=0x f^{\prime}(x)+2024 f(x)=0
  • B xf′(x)−2023f(x)=0x f^{\prime}(x)-2023 f(x)=0
  • C xf′(x)−2024f(x)=0x f^{\prime}(x)-2024 f(x)=0
  • D xf′(x)+f(x)=2024x f^{\prime}(x)+f(x)=2024

Step-by-Step Verified Solution

f(xy)=f(x)f(y)f\left(\frac{x}{y}\right)=\frac{f(x)}{f(y)}

amp;f′(1)=2024amp;f(1)=1\begin{aligned}& \mathrm{f}^{\prime}(1)=2024 \\& \mathrm{f}(1)=1\end{aligned}

Partially differentiating w. r. t. x

amp;f′(xy)⋅1y=1f(y)f′(x)amp;y→xamp;f′(1)⋅1x=f′(x)f(x)amp;2024f(x)=xf′(x)⇒xf′(x)−2024 f(x)=0\begin{aligned}& \mathrm{f}^{\prime}\left(\frac{\mathrm{x}}{\mathrm{y}}\right) \cdot \frac{1}{\mathrm{y}}=\frac{1}{\mathrm{f}(\mathrm{y})} \mathrm{f}^{\prime}(\mathrm{x}) \\& \mathrm{y} \rightarrow \mathrm{x} \\& \mathrm{f}^{\prime}(1) \cdot \frac{1}{\mathrm{x}}=\frac{\mathrm{f}^{\prime}(\mathrm{x})}{\mathrm{f}(\mathrm{x})} \\& 2024 \mathrm{f}(\mathrm{x})=\mathrm{xf}^{\prime}(\mathrm{x}) \Rightarrow \mathrm{xf}^{\prime}(\mathrm{x})-2024 \mathrm{~f}(\mathrm{x})=0\end{aligned}

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