How to Graph Parabolas on a TI-84 Calculator

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The equation of a parabola is a second-degree polynomial, also known as a quadratic function. Scientists model many natural processes with parabolic curves. For instance, in physics, the equation of projectile motion is a second-degree polynomial. Use a TI-84 graphing calculator to draw parabolas quickly and accurately. With a TI-84 calculator, you do not have to convert the equation of the parabola from standard form to vertex form, or vice versa, in order to plot the function.

    Press the "Y=" key to open the function input menu on the TI-84.

    Enter the equation of the parabola in the field marked "Y1." For example, if you have an equation of a parabola in standard form such as 3x^2 + 2x + 7, enter the equation using the keys for numbers, the variable x and operation symbols. If you have an equation of a parabola in vertex form such as 4(x-3)^2 - 8, enter the equation using the number, variable, operation and parentheses keys.

    Press the "Graph" key to generate the curve on your TI-84 calculator's screen.

    Press the "Window" key to access the window size menu and adjust the viewing window as necessary. For example, the parabola 3x^2 + 2x + 7 is best viewed in a window in which Xmin = 0, Xmax = 20, Ymin = -10 and Ymax = 10. The default window settings on the TI-84 are Xmin = -10, Xmax = 10, Ymin = -10 and Ymax = 10.

    Tips

    • If the coefficients of the parabola are large numbers, set the viewing window limits to large numbers as well. For example, if you graph the parabola equation y = 40x^2 - 100x + 50, use the window settings Xmin = -100, Xmax = 100, Ymin = -100 and Ymax = 100.

About the Author

Nucreisha Langdon has written professionally since 1991. She has ghostwritten more than 20 romantic fantasy novels, while her nonfiction work has appeared in the "Gainesville Sun" and the "Austin Chronicle." Langdon holds a Bachelor of Science in mathematics and a Bachelor of Arts in English from the University of Florida.

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