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JEE Main 202329 JanuaryEvening Shift
Exam
JEE Main
Year
2023
Date
29 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2023 · 29 January · Evening Shift · Mathematics · Differential Equations

Let y = y ( x ) be the solution of the differential equation x _ e...

Let y=y(x)y = y ( x ) be the solution of the differential equation xlog⁡exdydx+y=x2log⁡ex,(x>1)x{\log}_{e}x\dfrac{dy}{dx} + y = {x}^{2}\log_{e}x, ( x > 1 ). If y(2)=2y ( 2 ) = 2, then y(e)y ( e ) is equal to

Options

  1. A4+e24\dfrac{4 + {e}^{2}}{4}
  2. B1+e24\dfrac{1 + {e}^{2}}{4}
  3. C2+e22\dfrac{2 + {e}^{2}}{2}
  4. D1+e22\dfrac{1 + {e}^{2}}{2}

Correct answer

A. 4+e24\dfrac{4 + {e}^{2}}{4}

Step-by-step solution

Given,

xlnxdydx+y=x2ln⁡xxlnx\dfrac{dy}{dx} + y = {x}^{2}\ln x

⇒dydx+yxlnx=x⇒ \dfrac{dy}{dx} + \dfrac{y}{xlnx} = x

This is a linear differential equation.

Now, finding integrating factor we get

I.F=e∫1xlnxdx=eln⁡(ln⁡x)=ln⁡xI . F = {e}^{∫ \dfrac{1}{xlnx}dx} = {e}^{\ln \left(\ln x\right)} = \ln x

Now, solution of the differential equation is given by

y×I.F=∫(x×I.F)dxy \times I . F = ∫ \left(x \times I . F\right)dx

⇒y×ln⁡x=∫xlnxdx⇒ y \times \ln x = ∫ xlnxdx

⇒y×ln⁡x=ln⁡x⋅x22−x24+c⇒ y \times \ln x = \ln x \cdot \dfrac{{x}^{2}}{2} - \dfrac{{x}^{2}}{4} + c

Now given y(2)=2y\left(2\right) = 2,

2×ln⁡2=ln⁡2⋅222−224+c2 \times \ln 2 = \ln 2 \cdot \dfrac{{2}^{2}}{2} - \dfrac{{2}^{2}}{4} + c

⇒c=1⇒ c = 1

So, equation will be y×ln⁡x=ln⁡x⋅x22−x24+1y \times \ln x = \ln x \cdot \dfrac{{x}^{2}}{2} - \dfrac{{x}^{2}}{4} + 1

Now finding y(e)y\left(e\right) we get,

y×lne=lne⋅e22−e24+1y \times lne = lne \cdot \dfrac{{e}^{2}}{2} - \dfrac{{e}^{2}}{4} + 1

⇒y×1=1⋅e22−e24+1⇒ y \times 1 = 1 \cdot \dfrac{{e}^{2}}{2} - \dfrac{{e}^{2}}{4} + 1

⇒y=4+e24⇒ y = \dfrac{4 + {e}^{2}}{4}

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