Find the following integral (using Integration by parts method)
`int x^3 e^x dx`

Explanation

To solve the integral \( \int x^3 e^x \, dx \) using the method of integration by parts, we follow these steps:

### Step 1: Identify \( u \) and \( dv \)
We choose:
- \( u = x^3 \) (which we will differentiate)
- \( dv = e^x \, dx \) (which we will integrate)

### Step 2: Differentiate \( u \) and Integrate \( dv \)
...