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.
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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.
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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.