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JEE Main 202311 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
11 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2023 · 11 April · Morning Shift · Mathematics · Differential Equations

Let y = y (x) be a solution curve of the differential equation, (1...

Let y=y(x)beasolutioncurvey = y \left(x\right) be a solution curve of thedifferentialequation,(1−x2y2)dx=ydx+xdythe differential equation, \left(1 - {x}^{2}{y}^{2}\right)dx = ydx + xdy, If the line x=1x = 1 intersects the curve y=y(x)aty = y \left(x\right) aty = 2 and the line x=2x = 2 intersects the curve y=y(x)y = y \left(x\right) at y=αy = \alpha, then a value of α\alpha is

Options

  1. A\dfrac{1 - 3{e}^{2}}{2\left(3{e}^{2} + 1\right)}
  2. B\dfrac{1 + 3{e}^{2}}{2\left(3{e}^{2} - 1\right)}
  3. C\dfrac{3{e}^{2}}{2\left(3{e}^{2} - 1\right)}
  4. D\dfrac{3{e}^{2}}{2\left(3{e}^{2} + 1\right)}

Correct answer

B. \dfrac{1 + 3{e}^{2}}{2\left(3{e}^{2} - 1\right)}

Step-by-step solution

Given,

(1−x2y2)dx=ydx+xdy\left(1 - {x}^{2}{y}^{2}\right)dx = ydx + xdy

⇒dx=ydx+xdy1−(xy)2⇒ dx = \dfrac{ydx + xdy}{1 - {\left(xy\right)}^{2}}

⇒dx=d(yx)1−(xy)2⇒ dx = \dfrac{d\left(yx\right)}{1 - {\left(xy\right)}^{2}}

⇒dx=12(d(xy)1−xy+d(xy)1+xy)⇒ dx = \dfrac{1}{2}\left(\dfrac{d\left(xy\right)}{1 - xy} + \dfrac{d\left(xy\right)}{1 + xy}\right)

Now integrating both side we get,

⇒2x+c=ln⁡∣1+xy1−xy∣⇒ 2x + c = \ln \left|\dfrac{1 + xy}{1 - xy}\right|

⇒∣xy+1xy−1∣=ece2x⇒ \left|\dfrac{xy + 1}{xy - 1}\right| = {e}^{c}{e}^{2x}

Now given, y(1)=2y\left(1\right) = 2 so putting the value in above equation we get,

3=ece23 = {e}^{c}{e}^{2}

⇒ec=3e2⇒ {e}^{c} = \dfrac{3}{{e}^{2}}

Hence, the equation becomes ∣xy+1xy−1∣=3e2x−2\left|\dfrac{xy + 1}{xy - 1}\right| = 3{e}^{2x - 2}

Now finding y(2)y\left(2\right) so putting x=2x = 2 in above equation we get,

\left|\dfrac{2y + 1}{2y - 1}\right| = 3{e}^{2}</p><p></p><p>⇒ 2y + 1 = 2 \cdot 3{e}^{2}y - 3{e}^{2}</p><p></p><p>⇒ 1 + 3{e}^{2} = 2y\left(3{e}^{2} - 1\right)</p><p></p><p>⇒ y\left(2\right) = \dfrac{1 + 3{e}^{2}}{2\left(3{e}^{2} - 1\right)}

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