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Particular solution of the differential equation x(1+y2)dx−y(1+x2)dy=0x(1 + y^2)dx - y(1 + x^2)dy = 0, given y=0y = 0 when x=1x = 1, is

Solution

✅ Correct Option: 1

Given differential equation: x(1+y2)dx−y(1+x2)dy=0x(1 + y^2)dx - y(1 + x^2)dy = 0

Initial condition: When x=1x = 1, y=0y = 0


x(1+y2)dx=y(1+x2)dyx(1 + y^2)dx = y(1 + x^2)dy

x1+x2dx=y1+y2dy\frac{x}{1 + x^2}dx = \frac{y}{1 + y^2}dy


∫x1+x2dx=∫y1+y2dy\int \frac{x}{1 + x^2}dx = \int \frac{y}{1 + y^2}dy

For the left side, let u=1+x2u = 1 + x^2, then du=2x dxdu = 2x \, dx:

∫x1+x2dx=12∫1udu=12ln⁡∣1+x2∣\int \frac{x}{1 + x^2}dx = \frac{1}{2}\int \frac{1}{u}du = \frac{1}{2}\ln|1 + x^2|

Similarly:

∫y1+y2dy=12ln⁡∣1+y2∣\int \frac{y}{1 + y^2}dy = \frac{1}{2}\ln|1 + y^2|


12ln⁡(1+x2)=12ln⁡(1+y2)+C\frac{1}{2}\ln(1 + x^2) = \frac{1}{2}\ln(1 + y^2) + C

ln⁡(1+x2)=ln⁡(1+y2)+2C\ln(1 + x^2) = \ln(1 + y^2) + 2C

ln⁡(1+x2)−ln⁡(1+y2)=2C\ln(1 + x^2) - \ln(1 + y^2) = 2C

ln⁡(1+x21+y2)=2C\ln\left(\frac{1 + x^2}{1 + y^2}\right) = 2C

1+x21+y2=e2C=A\frac{1 + x^2}{1 + y^2} = e^{2C} = A

(1+x2)=A(1+y2)(1 + x^2) = A(1 + y^2)


When x=1x = 1, y=0y = 0:

(1+12)=A(1+02)(1 + 1^2) = A(1 + 0^2)

2=A2 = A


(1+x2)=2(1+y2)(1 + x^2) = 2(1 + y^2)

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