## Introduction: Quadratic Formula for the TI-83 and 84

Have you ever wondered if there is a way to make your calculator solve quadratic equations for you? Well, there is a fairly easy way to make your calculator do all the work for you.

Another program that I have put on Instructables is Heron's Formula.

www.instructables.com/id/Herons-Formula-program-for-the-TI-83-and-84/

## Step 1: Getting Started

You should know that a quadratic equation looks something like this: x^2-3x+2=0 or **ax^2+bx+c=0. **This will be important later on.

The first step is to press the program button on your calculator. Press the *right arrow *twice to get to new and select create new. Enter a name.

Now press *program* again and press the *right arrow* then press 2. To get letters, push the *alhpa* button. Now enter *A,B,C *and hit enter.

## Step 2: The Equation

Look at the first picture and put that on your calculator. Make sure you use the *negative* button before the first b! The -> is the store button. Press *sto-> *to get that. This just makes the equation equal to x. You may have noticed that this is only plus the square root of b squared... There is no button on this calculator for plus or minus so you will have to enter it as two separate equations.

Refer to the second picture for the second part of the equation. It is just like the first part except for a couple things.

## Step 3: Displaying Results

Press *program*, then the *right arrow*, then *3*. This will make the calculator display the answers. First open quotes (*alpha*, *+*) then put in 12 spaces (space is *alpha* then *0*) *x=* and close quotes. The equal sign is found by pressing *2nd* and then *math (test). *Then enter *,x,y* . (Hint: Press *2nd* then *alpha* to make it easier to type letters.) You can look at the picture if you need help. Make sure that you have the exact same thing as the picture below.

## Step 4: Using the Program

To exit out of this **do not hit clear!!! **This will delete everything on the line! Make sure you hit *2nd* then *mode (quit).*

Now push *program* and select the one you just made. Hit *enter* and type in the value of A. Then do this for B and C. Remember ax^2+bx+c=0. Example: x^2-3x+2=0; A=**1**, B=**-3** (use negative sign if necessary), C=**2. **The bold numbers are the numbers that you would enter in your program. After you enter all three variables hit *enter* and you get your answer.

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## 54 Comments

Thanks, too lazy to work this out on my own and really didnt want to waste time solving quadratics on a test.

I've checked the program for any errors, and as far as I can tell, the programs match. However, after I select the program and press enter, I get "ERR: ARCHIVED." What could be wrong?

That means that the program is archived, which prevents it from being deleted, but also used. You need to go into memory (press 2nd, then + sign), go to option 6 (unarcharchive), then press enter. Then go to your programs, select the program you are trying to use, and press enter. Press enter again, and it will be unarchived.

I have a TI-84, followed the instructions, and added parenthesis' around the variables to ensure I got correct answers with more complicated numbers. Works great, thanks!

2x^2-x-1 isn't x=4,-2

Put 2A in parentheses

If this is not working for you try putting 2A in paretheses

Hello I am getting incorrect answers. When i type in A=1, B=3,C=-4 I get 1 and 7.5 and that's incorrect

following the script, double and triple checking, and using the test variables, my answers are x=2,-1.5

is this correct?

What were the test variables that you used? If you used A = 1, B = -3, and C=2 like I did in step 4 then you should get 2 and 1 for the answers.