Q36 / 75 · JEE Main 2020 (07 Jan Shift 2) · Mathematics

Let y=yx be the solution curve of the differential equation, y2-xdydx=1 , satisfying y0=1 . This curve intersects the X-axis at a point whose abscissa is

  • Correct answer
    A
    2-e
  • B
    -e
  • C
    2
  • D
    2+e

Solution

dxdy+x=y2

This equation is a linear differential equation of the type dxdy+Px=Q, where P=1 and Q=y2.
Integrating Factor I.F. =e∫1dy=ey

Now solution of the differential equation is xI.F.=∫PI.F.dy+C
x·ey=∫y2·ey·dy=y2·ey-∫2y·ey·dy

⇒ x·ey=y2·ey-2y·ey+2ey+c

⇒ x=y2-2y+2+c·e-y

Put x=0, y=1

⇒ 0=1-2+2+ce

⇒ c=-e

Hence x=y2-2y+2+-e·e-y

On putting y=0 we get x=0-0+2+-ee-0

⇒ x=2-e

Hence, the correct answer is option: 'A'.

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