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The solution of the differential equation xdy−ydx=0xdy - ydx = 0 represents

Solution

✅ Correct Option: 1

The differential equation is xdy−ydx=0xdy - ydx = 0

Move ydxydx to the right side:

xdy=ydxxdy = ydx

Divide both sides by xyxy:

dyy=dxx\frac{dy}{y} = \frac{dx}{x}


Integrate both sides:

∫dyy=∫dxx\int \frac{dy}{y} = \int \frac{dx}{x}

ln⁡∣y∣=ln⁡∣x∣+C\ln|y| = \ln|x| + C

where CC is the constant of integration.


ln⁡∣y∣−ln⁡∣x∣=C\ln|y| - \ln|x| = C

Using the logarithm property ln⁡(a)−ln⁡(b)=ln⁡(a/b)\ln(a) - \ln(b) = \ln(a/b):

ln⁡∣yx∣=C\ln\left|\frac{y}{x}\right| = C


Taking exponential on both sides:

∣yx∣=eC\left|\frac{y}{x}\right| = e^C

Since eCe^C is a positive constant, let eC=ke^C = k where k>0k > 0:

yx=±k\frac{y}{x} = \pm k

Let ±k=m\pm k = m where mm is any constant:

yx=m\frac{y}{x} = m

y=mxy = mx


The equation y=mxy = mx represents a straight line with slope mm and yy-intercept 00.

Therefore, the solution represents a straight line passing through the origin.

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