Quadratic Formula for the TI-83 and 84




Posted in HomeLife-skills

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.

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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    Mine says Err:NONREAL ANS anyone got any idea of what I can do to fix is?

    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?

    1 reply

    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!

    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?

    1 reply

    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.

    It moves the X= to the right side of the screen (check out the last picture). Its not necessary, just a personal preference.

    I did everything exactly like the instructions said but I get the Syntax error on my TI 84 Plus C silver edition. I made sure that all of the numbers and letters correctly and also checked the negative to make sure I was using negative sign not the minus sign.

    1 reply

    mine did that, but it was because i'd put a comma after the C. i took it off and it was fine.

    Hey there! I have been using this for a few weeks, and it has been working fine, but I just tired using it again and it is saying i have a syntax error with a parentheses, but i have not erased anything and it looks exactly how your pictures look. Do you know what the problem is?

    Thanks a lot man! :)