# Determine the Values of R for Which the Given Differential Equation Has Solutions of the Form

Determining the Values of R for Which the Given Differential Equation Has Solutions of the Form

Differential equations play a crucial role in various fields of science and engineering, providing a mathematical framework to describe the behavior of dynamic systems. Often, we are interested in finding the solutions of these equations that exhibit a specific form. In this article, we will explore how to determine the values of R for which a given differential equation has solutions of a particular form. We will also include a frequently asked questions (FAQs) section at the end to address common queries related to this topic.

To begin, let’s consider a second-order linear homogeneous differential equation of the form:

y” + p(x)y’ + q(x)y = 0

where p(x) and q(x) are continuous functions of x. We aim to find solutions of the above equation that have a specific form, commonly referred to as the trial solution. For this purpose, we assume that the trial solution is of the form:

y(x) = e^(rx)

where r is a constant to be determined. Substituting this form into the differential equation, we obtain:

r^2 e^(rx) + p(x)re^(rx) + q(x)e^(rx) = 0

Factoring out the common term e^(rx), we have:

e^(rx)(r^2 + p(x)r + q(x)) = 0

Since e^(rx) is never zero, we can divide through by it, resulting in a characteristic equation:

r^2 + p(x)r + q(x) = 0

Solving this characteristic equation yields the values of r for which the given differential equation has solutions of the form e^(rx). The roots of this equation can be real or complex, depending on the nature of p(x) and q(x).

Now, let’s consider an example to illustrate the process of determining the values of R for which the differential equation has solutions of a specific form. Suppose we have the following differential equation:

y” + 4y’ + 4y = 0

We assume a trial solution of the form y(x) = e^(rx) and substitute it into the equation:

r^2 e^(rx) + 4re^(rx) + 4e^(rx) = 0

Factoring out e^(rx), we have:

e^(rx)(r^2 + 4r + 4) = 0

Dividing through by e^(rx), we obtain the characteristic equation:

r^2 + 4r + 4 = 0

Solving this quadratic equation, we find that it has a repeated root of -2. Therefore, the differential equation has solutions of the form:

y(x) = C1 e^(-2x) + C2 x e^(-2x)

where C1 and C2 are arbitrary constants.

FAQs:

Q: How do I determine the values of R for which the given differential equation has solutions of a specific form?
A: To determine the values of R, we assume a trial solution of the desired form and substitute it into the differential equation. This leads to a characteristic equation, which can be solved to find the values of R.

Q: Can the roots of the characteristic equation be complex?
A: Yes, the roots of the characteristic equation can be complex, depending on the nature of the coefficients in the differential equation.

Q: What if the characteristic equation has repeated roots?
A: If the characteristic equation has repeated roots, the differential equation will have solutions that include powers of x multiplied by the corresponding exponential function.

Q: Are there any other methods to find the values of R for a given differential equation?
A: Yes, there are other methods such as the method of undetermined coefficients and the method of variation of parameters. These methods provide alternative approaches to finding solutions of a specific form.

In conclusion, determining the values of R for which a given differential equation has solutions of a specific form involves assuming a trial solution, substituting it into the differential equation, and solving the resulting characteristic equation. The roots of this equation determine the values of R, which lead to the desired solutions. Keep in mind that the nature of the roots can be real or complex, depending on the coefficients of the differential equation.