Quadratic inequalities are polynomial inequalities of degree 2. You solve them using sign charts. This is how to do it:
Rule
Example 1
Solve the inequality
You can factorize this by using the quadratic formula:
Next, you make a sign chart:
You can read off that when . Because we had a greater than or equal sign () in the original inequality, the intervals are closed on the side that does not tend to infinity.