Here you will learn what is differential equation and degree and order of differential equation with examples.

Let’s begin –

## Differential Equation

An equation containing an independent variable, dependent variable and differential coefficients of dependent variable with respect to independent variable is called a differential equation.

**for example** : \(dy\over dx\) = 2xy and \(d^2y\over dx^2\) = 4x are examples of differential equations.

## Degree and Order of Differential Equation

**Order of Differential Equation**

The order of a differential equation is the order of the highest order derivative appearing in the equation.

**Example 1** : In the equation \(d^2y\over dx^2\) + 3\(dy\over dx\) + 2y = \(e^x\), the order of highest order derivative is 2. So, it is a differential equation of order 2.

**Example 2** : In the equation \(d^3y\over dx^3\) – 6\(({dy\over dx})^2\) – 4y = 0, the order of highest order derivative is 3. So, it is a differential equation of order 3.

**Degree of Differential Equation**

The degree of a differential equation is the degree of the highest order derivative, when differential coefficients are made free from radicals and fractions.

**Example 1** : In the equation \(d^3y\over dx^3\) – 6\(({dy\over dx})^2\) – 4y = 0, the power of highest order derivative is 1. So, it is a differential equation of degree 1.

**Example 2** : Consider the differential equation x\(({d^3y\over dx^3})^2\) – 6\(({dy\over dx})^4\) + \(y^4\) = 0.

**Solution** : In this equation, the order of the highest order derivative is 3 and its power is 2. So, it is a differential equation of order 3 and degree 2.

**Example 3** : Consider the differential equation \(({1 + ({dy\over dx})^2})^{3/2}\) = k\({d^2y\over dx^2}\).

**Solution** : The order of highest order differential coefficient is 2. So, its order is 2.

To find its degree we express the differential equation as a polynomial in derivatives. When expressed as a polynomial in derivatives it becomes \(k^2\)\(({d^2y\over dx^2})^2\) – \(({1 + ({dy\over dx})^2})^3\) = 0. Clearly, the power of the highest order differential coefficient is 2. So, its degree is 2.