The only new rule comes from multiplying or dividing by a negative number.

So whenever we divide or multiply by a negative number we must reverse the inequality. It is easy to forget to do this so take special care to watch out for negative coefficients.

**and**

*graphing them on a number line***.**

*interval notation***Note**: We use the following symbol to denote infinity:

**Tip**: Always use round parentheses and open dots for inequalities without the equal and always use square brackets and closed dots for inequalities with the equal.

**Video Examples on YouTube:**