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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Mathematics
Chapter
Differentiation

NTA Abhyas 2020 · Mathematics · Differentiation

If l n (x + y) = 2 x y ,then y^ ′ (0) is equal to

If ln(x+y)=2xy,theny′(0)isequalto</p>\text{l} \text{n} \left(x + y\right) = 2 x y \text{,}then y^{′} \left(0\right) is equal to</p>

Options

  1. A11
  2. B−1- 1
  3. C22
  4. D00

Correct answer

A. 11

Step-by-step solution

Given equation is ln⁡(x+y)=2xy\ln( x + y ) = 2xy...(1)

For x=0x = 0

ln⁡(0+y)=2.0.y=0\ln( 0 + y ) = 2.0.y = 0

⇒ln⁡y=0⇒ \ln y = 0

⇒y=1⇒ y = 1

Now, differentiating (1), we get,

1(x+y)(1+dydx)=2y+2xdydx1\left(x + y\right)\left(1 + \dfrac{dy}{dx}\right) = 2y + 2x\dfrac{dy}{dx}

At point (0,1), we get,

\left(\dfrac{1}{0 + 1}\right)\left(1 + \dfrac{dy}{dx}\right) =2 \left(1\right)+2+ 2\text{.} }}0\text{.}\left(\dfrac{dy}{dx}\right)<br/><br/><br /><br />⇒ 1 + \dfrac{dy}{dx} =2<br/><br/><br /><br />⇒ \dfrac{dy}{dx} =1= y^{'}( 0 )
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