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JEE Main 202315 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
15 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2023 · 15 April · Morning Shift · Mathematics · Differential Equations

Let x = x (y) be the solution of the differential equation 2(y + 2)...

Let x=xx = x\left(y\right)bethesolutionofthedifferentialequationbe the solution of the differential equation2\left(y + 2\right)\log_{e}\left(y + 2\right)dx + \left(x + 4 - 2\log_{e}\left(y + 2\right)\right)dy = 0,,y > - 1withwithx\left({e}^{4} - 2\right) = 1.Then. Thenx\left({e}^{9} - 2\right) is equal to

Options

  1. A33
  2. B49\dfrac{4}{9}
  3. C329\dfrac{32}{9}
  4. D103\dfrac{10}{3}

Correct answer

C. 329\dfrac{32}{9}

Step-by-step solution

Given,

2(y+2)log⁡e(y+2)dx+(x+4−2log⁡e(y+2))dy=02\left(y + 2\right)\log_{e}\left(y + 2\right)dx + \left(x + 4 - 2\log_{e}\left(y + 2\right)\right)dy = 0

Let x+4=u,y+2=vx + 4 = u, y + 2 = v

dx=du,dy=dvdx = du, dy = dv

So, the equation becomes,

\left(2vlnv\right)du = - \left(u - 2\ln v\right)dv</p><p></p><p>⇒ 2vlnv\dfrac{du}{dv} + u = 2\ln v</p><p></p><p>⇒ \dfrac{du}{dv} + \dfrac{1}{2vlnv} . u = \dfrac{1}{v}</p><p>Whichisalineardifferentialequation,</p><p>So,</p><p>Which is a linear differential equation,</p><p>So,IF = {e}^{\dfrac{1}{2} ∫ \dfrac{1}{vlnv}} = {e}^{\dfrac{1}{2}\ln \left(\ln v\right)} = \left(\ln v\right)\dfrac{1}{2}</p><p>Nowsolutionofdifferentialequationisgivenby,</p><p></p><p>Now solution of differential equation is given by,</p><p>u \cdot \left(\ln v\right)\dfrac{1}{2} = ∫ \dfrac{1}{v} \cdot \left(\ln v\right)\dfrac{1}{2}dv</p><p></p><p>⇒ u \cdot \left(\ln v\right)\dfrac{1}{2} = \dfrac{2}{3}\left(\ln v\right)\dfrac{3}{2} + c . . . . . . . \left(i\right)</p><p>Nowusinggivenvalue,</p><p>Now using given value,y = {e}^{4} - 2 ⇒ x = 1</p><p></p><p>∴ v = {e}^{4} ⇒ u = 5</p><p></p><p>5 \cdot \left(4\dfrac{1}{2}\right) = \dfrac{2}{3} \cdot \left(4\right)\dfrac{3}{2} + c</p><p></p><p>⇒ 10 = \dfrac{16}{3} + c</p><p></p><p>⇒ c = \dfrac{14}{3}</p><p>Nowfinding,</p><p>Now finding,y = {e}^{9} - 2 ⇒ v = y + 2 = {e}^{9}</p><p>Nowputtingthevalueinequation(i)</p><p>Now putting the value in equation \left(i\right) we get,

⇒u⋅3=23×27+143=18+143⇒ u \cdot 3 = \dfrac{2}{3} \times 27 + \dfrac{14}{3} = 18 + \dfrac{14}{3}

⇒x+4=u=6+149⇒ x + 4 = u = 6 + \dfrac{14}{9}

⇒x=2+149=329⇒ x = 2 + \dfrac{14}{9} = \dfrac{32}{9}

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