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Find the equation of a curve passing through origin and satisfying the differential equation dydx(1+x2)dydx+2xy = 4x2 - Mathematics

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Question

Find the equation of a curve passing through origin and satisfying the differential equation `(1 + x^2) "dy"/"dx" + 2xy` = 4x2 

Sum
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Solution

Given equation is `(1 + x^2) "dy"/"dx" + 2xy` = 4x2 

⇒ `"dy"/"dx" + (2x)/(1 + x^2) * y = (4x^2)/(1 + x^2)`

Here, P = `(2x)/(1 + x^2)` and Q = `(4x^2)/(1 + x^2)`

Integrating factor I.F. = `"e"^(int Pdx)`

= `"e"^(int (2x)/(1 + x^2) dx)`

= `"e"^(log(1 + x^2)`

= 1 + x2

∴ Solution is `y xx "I"."F". = int "Q" xx "I"."F".  "d"x + "c"`

⇒ `y(1 + x^2) = int (4x^2)/(1 + x^2) xx (1 + x^2) "d"x + "c"`

⇒ `y(1 + x^2) = int 4x^2 "d"x + "c"`

⇒ `y(1 + x^2) = 4/3 x^3 + "c"`  ......(i)

Since the curve is passing through origin i.e., (0, 0)

∴ Put y = 0 and x = 0 in equation (i)

0(1 + 0) = `4/3(0)^3 + "c"`

⇒ C = 0

∴ Equation is `y(1 + x^2) = 4/3 x^3`

⇒ y = `(4x^3)/(3(1 + x^2))`

Hence, the required solution is y =  `(4x^3)/(3(1 + x^2))`.

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Chapter 9: Differential Equations - Exercise [Page 194]

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NCERT Exemplar Mathematics [English] Class 12
Chapter 9 Differential Equations
Exercise | Q 15 | Page 194

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