# 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.

#### Step 1

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."

#### Step 2

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

#### Step 3

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.