# Solve the Differential Equation y'' - 9y = 54 using the Annihilator Method | Summary and Q&A

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October 17, 2020
by
The Math Sorcerer
Solve the Differential Equation y'' - 9y = 54 using the Annihilator Method

## TL;DR

This video explains how to solve a differential equation using the annihilator method, which involves finding the characteristic equation, applying an annihilator operator, and determining the particular solution.

## Key Insights

• 🟰 The annihilator method involves pretending the differential equation is equal to zero and finding the characteristic equation.
• 🫱 Annihilating the right-hand side using an appropriate operator simplifies the equation to a new differential equation.
• 👶 Solving the new differential equation yields the complementary function and the form of the particular solution.
• ❓ The particular solution is obtained by differentiating and substituting back into the original equation.
• 🍹 The final solution is the sum of the complementary function and particular solution.
• 💁 This method eliminates the need for guessing the form of the particular solution.
• 💁 The steps in the annihilator method are similar to other differential equation solving methods, but with the advantage of providing the form of the particular solution.

## Transcript

in this problem we're going to solve this differential equation using the annihilator method so this first step will be to pretend that this differential equation is equal to zero so we have y double prime minus 9y and that's equal to 0. to solve this we'll write down what's called the characteristic equation so because it's a second derivative we ... Read More

### Q: What is the first step in solving the differential equation using the annihilator method?

The first step is to pretend that the differential equation is equal to zero and write down the characteristic equation by factoring the terms involving derivatives.

### Q: What does the complementary function represent in the context of solving a differential equation?

The complementary function, denoted as yc, is the solution that arises from treating the differential equation as a homogeneous equation (equal to zero) and solving for the values of constants.

### Q: How does the annihilator method help in solving a differential equation?

The annihilator method involves applying an operator (in this case, the derivative) to both sides of the equation to annihilate the right-hand side and create a new differential equation.

### Q: What is the role of the particular solution in solving the differential equation?

The particular solution, denoted as yp, completes the final answer by providing the missing part that was not covered by the complementary function yc. It is found by differentiating and substituting back into the original equation.

## Summary & Key Takeaways

• The video demonstrates the process of solving a second-order differential equation by pretending it is equal to zero and finding the characteristic equation.

• The annihilator method is introduced as a way to eliminate the right-hand side of the equation, resulting in a new differential equation.

• By factoring and solving the new differential equation, the complementary function and particular solution can be determined, leading to the final answer.