**Unformatted text preview: **on must have at least one zero in between.
Graphically, this means that a parabola can’t be above the x-axis at one point and below the x-axis
at another point without crossing the x-axis. This allows us to determine the sign of all of the
function values on a given interval by testing the function at just one value in the interval. This
gives us the following. 1 We will give this property a name in Chapter 3 and revisit this concept then. 2.4 Inequalities 161
Steps for Solving a Quadratic Inequality 1. Rewrite the inequality, if necessary, as a quadratic function f (x) on one side of the inequality
and 0 on the other.
2. Find the zeros of f and place them on the number line with the number 0 above them.
3. Choose a real number, called a test value, in each of the intervals determined in step 2.
4. Determine the sign of f (x) for each test value in step 3, and write that sign above the
corresponding interval.
5. Choose the intervals which correspond to the correct sign to solve the inequality. Exa...

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