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# Solution for Find D Y D X in Each of the Following Cases 4 X + 3 Y = Log ( 4 X − 3 Y ) ? - CBSE (Science) Class 12 - Mathematics

ConceptSimple Problems on Applications of Derivatives

#### Question

Find  $\frac{dy}{dx}$ in each of the following cases  $4x + 3y = \log \left( 4x - 3y \right)$ ?

#### Solution

$\text{We have}, 4x + 3y = \log\left( 4x - 3y \right)$

Differentiating with respect to x, we get,

$\frac{d}{dx}\left( 4x \right) + \frac{d}{dx}\left( 3y \right) = \frac{d}{dx}\left\{ \log\left( 4x - 3y \right) \right\}$
$\Rightarrow 4 + 3\frac{d y}{d x} = \frac{1}{\left( 4x - 3y \right)}\frac{d}{dx}\left( 4x - 3y \right)$
$\Rightarrow 4 + 3\frac{d y}{d x} = \frac{1}{\left( 4x - 3y \right)}\left( 4 - 3\frac{d y}{d x} \right)$
$\Rightarrow 3\frac{d y}{d x} + \frac{3}{\left( 4x - 3y \right)}\frac{d y}{d x} = \frac{4}{\left( 4x - 3y \right)} - 4$
$\Rightarrow 3\frac{d y}{d x}\left\{ 1 + \frac{1}{\left( 4x - 3y \right)} \right\} = 4\left\{ \frac{1}{\left( 4x - 3y \right)} - 1 \right\}$
$\Rightarrow 3\frac{d y}{d x}\left\{ \frac{4x - 3y + 1}{\left( 4x - 3y \right)} \right\} = 4\left\{ \frac{1 - 4x + 3y}{\left( 4x - 3y \right)} \right\}$
$\Rightarrow \frac{d y}{d x} = \frac{4}{3}\left\{ \frac{1 - 4x + 3y}{\left( 4x - 3y \right)} \right\}\left( \frac{4x - 3y}{4x - 3y + 1} \right)$
$\Rightarrow \frac{d y}{d x} = \frac{4}{3}\left( \frac{1 - 4x + 3y}{4x - 3y + 1} \right)$

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Solution Find D Y D X in Each of the Following Cases 4 X + 3 Y = Log ( 4 X − 3 Y ) ? Concept: Simple Problems on Applications of Derivatives.
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