Home
Class 12
MATHS
STATEMENT -1 : The differential equation...

STATEMENT -1 : The differential equation `(dy)/(dx) = (2xy)/(x^(2) + y^(2))` Can't be solved by the substitution x = vy.
and
STATEMENT-2 : When the differential equation is homogeneous of first order and first degree, then the substitution that solves the equation is y = vx.

A

Statement-1 is true, Statement-2 is true, Statement-2 is a correct explanation for Statement-1.

B

Statement-1 is true, Statement-2 is true, Statement-2 is NOT a correct explanation for Statement-1.

C

Statement-1 is True, Statement-2 is False

D

Statement-1 is False, Statement-2 is True

Text Solution

AI Generated Solution

The correct Answer is:
To solve the given differential equation and analyze the statements, let's proceed step by step. ### Step 1: Identify the Differential Equation The given differential equation is: \[ \frac{dy}{dx} = \frac{2xy}{x^2 + y^2} \] ### Step 2: Check if the Equation is Homogeneous A differential equation is homogeneous if it can be expressed in the form \( \frac{dy}{dx} = f\left(\frac{y}{x}\right) \). To check if it's homogeneous, we can rewrite the right-hand side: \[ \frac{2xy}{x^2 + y^2} = \frac{2 \cdot \frac{y}{x} \cdot x^2}{x^2 + \left(\frac{y}{x} \cdot x\right)^2} = \frac{2v}{1 + v^2} \] where \( v = \frac{y}{x} \). Since we can express the equation in terms of \( v \), it confirms that the equation is homogeneous. ### Step 3: Use the Substitution \( y = vx \) To solve the equation, we use the substitution \( y = vx \), where \( v \) is a function of \( x \). Then, we differentiate \( y \) with respect to \( x \): \[ \frac{dy}{dx} = v + x\frac{dv}{dx} \] ### Step 4: Substitute into the Differential Equation Now, substitute \( y = vx \) and \( \frac{dy}{dx} = v + x\frac{dv}{dx} \) into the original equation: \[ v + x\frac{dv}{dx} = \frac{2x(vx)}{x^2 + (vx)^2} \] This simplifies to: \[ v + x\frac{dv}{dx} = \frac{2vx^2}{x^2(1 + v^2)} = \frac{2v}{1 + v^2} \] ### Step 5: Rearranging the Equation Rearranging gives us: \[ x\frac{dv}{dx} = \frac{2v}{1 + v^2} - v \] This can be further simplified to: \[ x\frac{dv}{dx} = \frac{2v - v(1 + v^2)}{1 + v^2} = \frac{v(1 - v^2)}{1 + v^2} \] ### Step 6: Separate Variables Now, we can separate variables: \[ \frac{1 + v^2}{v(1 - v^2)} dv = \frac{1}{x} dx \] ### Step 7: Integrate Both Sides Integrate both sides to find \( v \): \[ \int \frac{1 + v^2}{v(1 - v^2)} dv = \int \frac{1}{x} dx \] ### Step 8: Solve the Integrals The left-hand side can be solved using partial fractions, and the right-hand side integrates to \( \ln|x| + C \). ### Conclusion The substitution \( y = vx \) is valid for solving this homogeneous differential equation, contradicting Statement 1. Thus, Statement 1 is false, and Statement 2 is true.
Promotional Banner

Topper's Solved these Questions

  • DIFFERENTIAL EQUATIONS

    AAKASH INSTITUTE ENGLISH|Exercise Assignment Section - F (Matrix-Match Type Questions)|2 Videos
  • DIFFERENTIAL EQUATIONS

    AAKASH INSTITUTE ENGLISH|Exercise Assignment Section-G (Integer Answer Type Questions)|3 Videos
  • DIFFERENTIAL EQUATIONS

    AAKASH INSTITUTE ENGLISH|Exercise Assignment Section - D (Linked Comprehension Type Questions))|11 Videos
  • DETERMINANTS

    AAKASH INSTITUTE ENGLISH|Exercise SECTION - J|12 Videos
  • INTEGRALS

    AAKASH INSTITUTE ENGLISH|Exercise Try yourself|50 Videos

Similar Questions

Explore conceptually related problems

Solve the differential equation: (dy)/(dx)+y/x=x^2

Solve the differential equation dy/dx=2/(x+y)

Solve the differential equation : (dy)/(dx)-y/x=2x^2

Solve the differential equation: (dy)/(dx)+y=e^(-2x)

Solve the differential equation: (dy)/(dx)+y=e^(-2x)

Solve the differential equation (dy)/(dx) + 2y = x .

Solve the differential equation: (dy)/(dx)=y^2+2y+2

Solve the differential equation : (dy)/(dx)=(x^(2)-y^(2))/(xy) .

Solve the differential equation: (dy)/(dx)+2y=sin x

Solve the differential equation (dy)/(dx)=(x+2y-1)/(x+2y+1).