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JEE Main 202310 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
10 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2023 · 10 April · Morning Shift · Mathematics · Differential Equations

The slope of tangent at any point (x, y) on a curve y = y(x) is x ^...

The slope of tangent at any point (x,y)\left(x, y\right) on a curve y=y(x)y = y\left(x\right) is x2+y22xy,x>0\dfrac{{x}^{2} + {y}^{2}}{2xy}, x > 0. If y(2)=0y\left(2\right) = 0, then a value of y(8)y\left(8\right) is

Options

  1. A−42- 4\sqrt{2}
  2. B232\sqrt{3}
  3. C−23- 2\sqrt{3}
  4. D434\sqrt{3}

Correct answer

D. 434\sqrt{3}

Step-by-step solution

Given:

dydx=x2+y22xy\dfrac{dy}{dx} = \dfrac{{x}^{2} + {y}^{2}}{2xy}

Put y=vx⇒dydx=v+xdvdxy = vx ⇒ \dfrac{dy}{dx} = v + x\dfrac{dv}{dx}

v+xdvdx=1+v22vv + x\dfrac{dv}{dx} = \dfrac{1 + {v}^{2}}{2v}

⇒xdvdx=1−v22v⇒ x\dfrac{dv}{dx} = \dfrac{1 - {v}^{2}}{2v}

⇒∫(2vv2−1)dv=−∫dxx⇒ ∫ \left(\dfrac{2v}{{v}^{2} - 1}\right)dv = - ∫ \dfrac{dx}{x}

⇒log⁡e∣v2−1∣=log⁡e(Cx)⇒ \log_{e}\left|{v}^{2} - 1\right| = \log_{e}\left(\dfrac{C}{x}\right)

⇒y2−x2x2=Cx⇒ \dfrac{{y}^{2} - {x}^{2}}{{x}^{2}} = \dfrac{C}{x}

⇒y2−x2=Cx⇒ {y}^{2} - {x}^{2} = Cx

Put x=2x = 2 and y=0y = 0 we get,

0−22=2C⇒C=−20 - {2}^{2} = 2C ⇒ C = - 2

⇒y2=x2−2x⇒ {y}^{2} = {x}^{2} - 2x

⇒y(8)=82−16⇒ y\left(8\right) = \sqrt{{8}^{2} - 16}

⇒y(8)=48=43⇒ y\left(8\right) = \sqrt{48} = 4\sqrt{3}

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