How to Make a Quadratic Formula Program on a TI-84 Plus
The quadratic formula is a common way to find where a quadratic graph touches the "x" axis. Though a simple equation, the quadratic formula is long and plugging numbers into a calculator can be tedious. There is also the possibility of missing parentheses or misplacing negative signs. An effective way to combat these problems is by writing a quick equation to calculate the numbers.
Create a new program. On the calculator, press "PRGM" followed by the left arrow key. A menu will appear with one option, reading "Create New." Press "ENTER" and a new screen will appear, reading "PROGRAM" followed by "NAME=." Type in the desired title for the program and press "ENTER."
Type out the program. Pay very close attention to what is being typed, because any misplaced symbols will cause inaccurate calculations. The screen will show "PROGRAM:" followed by the given title. Beneath this will be a colon followed by a blinking cursor. Type the following, pressing "ENTER" at the end of each line. Each "ENTER" will bring the cursor to a new line, started by a colon. See the "Tips" section to find the locations of the commands not found on the keypad.Prompt A,B,C((-B+√((B)^2-(4AC)))/(2A))'D((-B-√((B)^2-(4AC)))/(2A))'EDisp "ZEROS"Disp DDisp E
Run your program to test it. Press "PRGM" and use the up and down arrow keys to highlight the new program and press "ENTER." A screen will appear displaying "prgm" followed by the given title. Press "ENTER" again and "A=?" will appear, followed by the cursor. For this test, type "1" and press "ENTER." "B=?" will appear - type "0" and "ENTER." Finally, "C=?" will appear; type "-1" and press "ENTER." The calculator will display "ZEROS" on the left side of the screen, followed by "1," "-1," and "Done" on the right. This means that the equation "x^2 - 1" touches the x-axis at x=1 and x=-1.