### Essential Concepts

- Any first-order linear differential equation can be written in the form [latex]y^{\prime} +p\left(x\right)y=q\left(x\right)[/latex].
- We can use a five-step problem-solving strategy for solving a first-order linear differential equation that may or may not include an initial value.
- Applications of first-order linear differential equations include determining motion of a rising or falling object with air resistance and finding current in an electrical circuit.

## Key Equations

**standard form**

[latex]y^{\prime} +p\left(x\right)y=q\left(x\right)[/latex]**integrating factor**

[latex]\mu \left(x\right)={e}^{\displaystyle\int p\left(x\right)dx}[/latex]

## Glossary

- integrating factor
- any function [latex]f\left(x\right)[/latex] that is multiplied on both sides of a differential equation to make the side involving the unknown function equal to the derivative of a product of two functions

- linear
- description of a first-order differential equation that can be written in the form [latex]a\left(x\right){y}^{\prime }+b\left(x\right)y=c\left(x\right)[/latex]

- standard form
- the form of a first-order linear differential equation obtained by writing the differential equation in the form [latex]y^{\prime} +p\left(x\right)y=q\left(x\right)[/latex]