Medium MCQ +4 / -1 PYQ · JEE Mains 2020

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

$\left( {{y^2} - x} \right){{dy} \over {dx}} = 1$, satisfying y(0) = 1. This curve intersects the x-axis at a point whose abscissa is :

  1. A 2 + e
  2. B -e
  3. C 2
  4. D 2 - e Correct answer

Solution

$\left( {{y^2} - x} \right){{dy} \over {dx}} = 1$ <br><br>$\Rightarrow$ ${{dx} \over {dy}}$ + x = y<sup>2</sup> <br><br>I.F = ${e^{\int {dy} }}$ = e<sup>y</sup> <br><br>Solution is given by <br><br>xe<sup>y</sup> = ${\int {{y^2}{e^y}dy} }$ <br><br>$\Rightarrow$ xe<sup>y</sup> = (y<sup>2</sup> – 2y + 2)e<sup>y</sup> + C <br><br>y(0) = 1 means x = 0, y = 1 <br><br>$\therefore$ C = -e <br><br>$\therefore$ xe<sup>y</sup> = (y<sup>2</sup> – 2y + 2)e<sup>y</sup> - e <br><br>put y = 0 <br><br>$\therefore$ x = 0 – 0 + 2 – e <br><br>$\Rightarrow$ x = 2 - e

About this question

Subject: Mathematics · Chapter: Differential Equations · Topic: Order and Degree

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