Question:

General solution of $y \frac{dy}{dx}+by^{2}=a\,cos\,x, 0 < x< 1$ is

Updated On: Jul 12, 2022
  • $y^{2} = 2a\left(2b\, sinx + cosx\right) + ce^{-2bx}$
  • $\left(4b^{2} + 1\right)y^{2} = 2a\left(sinx + 2bcosx\right) + ce^{-2bx}$
  • $\left(4b^{2} + 1\right)y^{2} = 2a\left(sinx + 2bcosx\right) + ce^{2bx}$
  • $y^{2} = 2a\left(2bsinx + cosx\right) + ce^{2bx}$
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The Correct Option is B

Solution and Explanation

Let $y^{2} = z$ $y \frac{dy}{dx}=\frac{1}{2} \frac{dz}{dx}$ $\frac{dz}{dx}+2bz=2a\,cos\,x$ $IF=e^{2b\int dx}=e^{2bx}$ $z.e^{2bx}=\int\,2a\,cos\,x.e^{2bx}. dx$ $y^{2}e^{2bx}=\frac{2a}{4b^{2}+1}\left(sin\,x+2b\,cos\,x\right)e^{2bx}+c$ $\left(4b^{2}+1\right)y^{2}=2a\left(sinx+2bcox\right)+ce^{-2bx}$
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Concepts Used:

Differential Equations

A differential equation is an equation that contains one or more functions with its derivatives. The derivatives of the function define the rate of change of a function at a point. It is mainly used in fields such as physics, engineering, biology and so on.

Orders of a Differential Equation

First Order Differential Equation

The first-order differential equation has a degree equal to 1. All the linear equations in the form of derivatives are in the first order. It has only the first derivative such as dy/dx, where x and y are the two variables and is represented as: dy/dx = f(x, y) = y’

Second-Order Differential Equation

The equation which includes second-order derivative is the second-order differential equation. It is represented as; d/dx(dy/dx) = d2y/dx2 = f”(x) = y”.

Types of Differential Equations

Differential equations can be divided into several types namely

  • Ordinary Differential Equations
  • Partial Differential Equations
  • Linear Differential Equations
  • Nonlinear differential equations
  • Homogeneous Differential Equations
  • Nonhomogeneous Differential Equations