Solving Quadratic Inequalities
Example: Solve 3x2 + 3x - 6 < 0
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Step 1: Go to ![]() 3x2 + 3x - 6. Press ![]() You are graphing a quadratic function , so the graph should be a parabola . |
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Step 2: You want to determine where the quadratic function is less than 0. So you need to look at the graph and determine what part of the graph lies below the x-axis or the line y = 0. |
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Step 3: The part of the graph that is below the x-axis is the part that lies between the x-intercepts. To find these x- intercepts or zeroes , go to ![]() menu, and select 2: zero . Press ![]() To find the intercept on the left , use the arrow keys to move the cursor to the left of the point, press ![]() Then move the cursor to the right of the point, press ![]() press ![]() The x-intercept is x= -2. |
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To find the intercept on the right, go to ![]() menu, and select 2: zero . Press ![]() Then repeat the process used above. The other intercept is x = 1. |
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Step 4: Remember - since you are solving an inequality , the solution will be an interval or the union of two intervals. The solution to this inequality is the interval (-2, 1) or -2 < x < 1. |
Step 5: If you want to determine where a quadratic is greater than 0, you need to look at the graph and determine what part of the graph lies above the x-axis. |
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