Up to this point we have been solving quadratic inequalities. The technique involving sign charts extends to solving polynomial inequalities of higher degree.
Step 1: Determine the critical numbers, which are the roots or zeros in the case of a polynomial inequality.
Step 2: Create a sign chart.
Step 3: Use the sign chart to answer the question.
Rational inequalities are solved using the same technique. The only difference is in the critical numbers. It turns out that the y-values may change from positive to negative at a restriction. So we will include the zeros of the denominator in our list of critical numbers.
Use open dots for all of the critical numbers when a strict inequality is involved.