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The solution of the equation (dy)/(dx) =...

The solution of the equation `(dy)/(dx) = (y^(2)-y-2)/(x^(2) +2x-3)` is

A

`(1)/(3) log |(y-2)/(y+1)| =(1)/(4) log |(x-1)/(x+3)|+c`

B

`(1)/(3) log |(y+1)/(y-3)|= (1)/(4) log |(x+3)/(x-1)|+c`

C

`(1)/(4) log |(y+1)/(y-2)| = (1)/(3) log |(x+3)/(x+1)|+c`

D

`log (y^(2)-y-2) = log (x^(2) + 2x-3)+c`

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The correct Answer is:
To solve the differential equation \[ \frac{dy}{dx} = \frac{y^2 - y - 2}{x^2 + 2x - 3}, \] we will follow these steps: ### Step 1: Factor the numerator and denominator First, we need to factor both the numerator \(y^2 - y - 2\) and the denominator \(x^2 + 2x - 3\). **Numerator:** \[ y^2 - y - 2 = (y - 2)(y + 1) \] **Denominator:** \[ x^2 + 2x - 3 = (x + 3)(x - 1) \] Thus, we can rewrite the equation as: \[ \frac{dy}{dx} = \frac{(y - 2)(y + 1)}{(x + 3)(x - 1)} \] ### Step 2: Separate the variables We can separate the variables by rearranging the equation: \[ \frac{dy}{(y - 2)(y + 1)} = \frac{dx}{(x + 3)(x - 1)} \] ### Step 3: Integrate both sides Next, we will integrate both sides. **Left Side:** To integrate \(\frac{1}{(y - 2)(y + 1)}\), we can use partial fractions: \[ \frac{1}{(y - 2)(y + 1)} = \frac{A}{y - 2} + \frac{B}{y + 1} \] Multiplying through by the denominator \((y - 2)(y + 1)\) gives: \[ 1 = A(y + 1) + B(y - 2) \] Setting \(y = 2\): \[ 1 = A(3) \implies A = \frac{1}{3} \] Setting \(y = -1\): \[ 1 = B(-3) \implies B = -\frac{1}{3} \] Thus: \[ \frac{1}{(y - 2)(y + 1)} = \frac{1/3}{y - 2} - \frac{1/3}{y + 1} \] Integrating gives: \[ \int \left( \frac{1/3}{y - 2} - \frac{1/3}{y + 1} \right) dy = \frac{1}{3} \ln |y - 2| - \frac{1}{3} \ln |y + 1| + C_1 \] **Right Side:** For the right side, we can similarly use partial fractions: \[ \frac{1}{(x + 3)(x - 1)} = \frac{C}{x + 3} + \frac{D}{x - 1} \] Following similar steps, we find: \[ \int \left( \frac{1/4}{x + 3} - \frac{1/4}{x - 1} \right) dx = \frac{1}{4} \ln |x + 3| - \frac{1}{4} \ln |x - 1| + C_2 \] ### Step 4: Combine results Setting the integrals equal to each other: \[ \frac{1}{3} \ln |y - 2| - \frac{1}{3} \ln |y + 1| = \frac{1}{4} \ln |x + 3| - \frac{1}{4} \ln |x - 1| + C \] ### Step 5: Simplify We can combine the logarithms: \[ \frac{1}{3} \ln \left( \frac{|y - 2|}{|y + 1|} \right) = \frac{1}{4} \ln \left( \frac{|x + 3|}{|x - 1|} \right) + C \] ### Step 6: Exponentiate to solve for y Exponentiating both sides gives: \[ \left( \frac{|y - 2|}{|y + 1|} \right)^{\frac{1}{3}} = K \left( \frac{|x + 3|}{|x - 1|} \right)^{\frac{1}{4}} \] where \(K = e^{3C}\). ### Final Solution Thus, the solution of the differential equation is: \[ \frac{|y - 2|}{|y + 1|} = K \left( \frac{|x + 3|}{|x - 1|} \right)^{\frac{3}{4}}. \]
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MTG-WBJEE-DIFFERENTIAL EQUATIONS-WB JEE Previous Years Questions
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  5. The curve y=(cosx+y)^(1/2) satisfies the differential equation :

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  17. The solution of the differential equation (dy)/(dx) + (y)/(x log(e)x)=...

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  18. General solution of y(dy)/(dx) + by^(2)=a cos x, 0 lt x lt 1 is

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