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JEE Main 202427 JanuaryEvening Shift
Exam
JEE Main
Year
2024
Date
27 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2024 · 27 January · Evening Shift · Mathematics · Differential Equations

If y = y ( x ) is the solution curve of the differential equation (...

If y=y(x)isthesolutioncurveofthedifferentialequation(x2−4)dy−(y2−3y)dx=0y = y ( x ) is the solution curve of the differential equation \left({x}^{2} - 4\right)dy - \left({y}^{2} - 3y\right)dx = 0, x>2,y(4)=32x > 2, y ( 4 ) = \dfrac{3}{2} and the slope of the curve is never zero, then the value of y(10)y ( 10 ) equals :

Options

  1. A31+(8)14\dfrac{3}{1 + ( 8{)}^{\dfrac{1}{4}}}
  2. B31+22\dfrac{3}{1 + 2\sqrt{2}}
  3. C31−22\dfrac{3}{1 - 2\sqrt{2}}
  4. D31−(8)14\dfrac{3}{1 - ( 8{)}^{\dfrac{1}{4}}}

Correct answer

A. 31+(8)14\dfrac{3}{1 + ( 8{)}^{\dfrac{1}{4}}}

Step-by-step solution

Given,

(x2−4)dy−(y2−3y)dx=0\left({x}^{2} - 4\right)dy - \left({y}^{2} - 3y\right)dx = 0

⇒∫dyy2−3y=∫dxx2−4⇒ ∫ \dfrac{dy}{{y}^{2} - 3y} = ∫ \dfrac{dx}{{x}^{2} - 4}

⇒13∫y−(y−3)y(y−3)dy=∫dxx2−4⇒ \dfrac{1}{3} ∫ \dfrac{y - ( y - 3 )}{y ( y - 3 )}dy = ∫ \dfrac{dx}{{x}^{2} - 4}

⇒13∫(1y−3−1y)dy=∫dxx2−22⇒ \dfrac{1}{3} ∫ \left(\dfrac{1}{y - 3} - \dfrac{1}{y}\right)dy = ∫ \dfrac{dx}{{x}^{2} - {2}^{2}}

⇒13(log∣y−3∣−log∣y∣)=14log⁡∣x−2x+2∣+C⇒ \dfrac{1}{3}\left(log | y - 3 | - log | y |\right) = \dfrac{1}{4}\log \left|\dfrac{x - 2}{x + 2}\right| + C

⇒13log⁡∣y−3y∣=14log⁡∣x−2x+2∣+C⇒ \dfrac{1}{3}\log \left|\dfrac{y - 3}{y}\right| = \dfrac{1}{4}\log \left|\dfrac{x - 2}{x + 2}\right| + C

At x=4,y=32x = 4, y = \dfrac{3}{2}

⇒13log⁡∣32−332∣=14log⁡∣4−24+2∣+C⇒ \dfrac{1}{3}\log \left|\dfrac{\dfrac{3}{2} - 3}{\dfrac{3}{2}}\right| = \dfrac{1}{4}\log \left|\dfrac{4 - 2}{4 + 2}\right| + C

⇒0=14log⁡∣13∣+C⇒ 0 = \dfrac{1}{4}\log \left|\dfrac{1}{3}\right| + C

⇒0=−log⁡∣3∣14+C⇒ 0 = - \log \left|3\right|\dfrac{1}{4} + C

⇒C=14log⁡(3)⇒ C = \dfrac{1}{4}\log \left(3\right)

⇒13log⁡∣y−3y∣=14log⁡∣x−2x+2∣+14log⁡(3)⇒ \dfrac{1}{3}\log \left|\dfrac{y - 3}{y}\right| = \dfrac{1}{4}\log \left|\dfrac{x - 2}{x + 2}\right| + \dfrac{1}{4}\log ( 3 )

Putting, x=10x = 10

⇒13log⁡∣y−3y∣=14log⁡∣23∣+14log⁡(3)⇒ \dfrac{1}{3}\log \left|\dfrac{y - 3}{y}\right| = \dfrac{1}{4}\log \left|\dfrac{2}{3}\right| + \dfrac{1}{4}\log ( 3 )

⇒13log⁡∣y−3y∣=14log⁡∣2∣⇒ \dfrac{1}{3}\log \left|\dfrac{y - 3}{y}\right| = \dfrac{1}{4}\log \left|2\right|

⇒log⁡∣y−3y∣=34log⁡2⇒ \log \left|\dfrac{y - 3}{y}\right| = \dfrac{3}{4}\log 2

⇒log⁡∣y−3y∣=log⁡(234)⇒ \log \left|\dfrac{y - 3}{y}\right| = \log \left(2\dfrac{3}{4}\right)

⇒−y+3=814⋅y⇒ - y + 3 = 8\dfrac{1}{4} \cdot y

⇒3=(814+1)y⇒ 3 = \left(8\dfrac{1}{4} + 1\right)y

⇒31+(8)14=y⇒ \dfrac{3}{1 + \left(8\right)\dfrac{1}{4}} = y

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