Final answer:
To find a particular solution of the given differential equation using the method of undetermined coefficients, assume the particular solution to be of the form A sin(3x) + B cos(3x) and solve for the coefficients.
Step-by-step explanation:
To find a particular solution of the given differential equation using the method of undetermined coefficients, we assume the particular solution to be of the form y_p = A sin(3x) + B cos(3x), where A and B are constants.
Next, we substitute the assumed solution into the differential equation and solve for the coefficients A and B. Taking the first and second derivatives of y_p, we substitute them back into the differential equation. This allows us to equate the coefficients of sin(3x) and cos(3x) on both sides of the equation and solve for A and B.
After finding the values of A and B, we substitute them back into the assumed solution y_p = A sin(3x) + B cos(3x), and that gives us the particular solution of the given differential equation.