To use Descartes' Rule of Signs to find how many positive and negative roots are in polynomial functions, just follow these easy steps:

1. Finding Positive Roots:

   • First, write down the polynomial.
   • Next, look at the signs of the numbers in the polynomial.
   • Count how many times the signs change as you move through the polynomial. Each time the sign changes, it means there could be a positive root.

2. Finding Negative Roots:

   • Now, let's look at what happens when we put negative values into the polynomial. This means looking at $f(-x)$.
   • Count the sign changes in $f(-x)$. This will show you how many negative roots could be there.

3. Counting Roots:

   • The number of positive or negative roots could be the number you counted, or it might be lower by an even number.

This is a smart way to figure out how many roots you might have without needing to solve the whole polynomial!