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.

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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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    69 Discussions


    4 days ago

    Many thanks for the effort you put in this!!!


    Question 27 days ago

    How do you get the = sign on your calculator? I can't find the option anywhere.

    1 answer

    Answer 4 days ago

    click 2nd then math button under alpha


    3 months ago

    These instructions are so easy to follow and helpful! Thank you!


    Question 4 months ago

    I've triple checked my programs and even added parentheses as suggested in comments but keep betting 2.618... & .3819.... as answers. Is there some other setting that is incorrect on this calculator that could be giving me incorrect computations?


    2 years ago

    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!

    1 reply

    1 year ago

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

    2 replies

    Reply 9 months ago

    The program on step 2 above has an error. The equation should have parentheses around the 2A. It's written correctly in step 3.

    Also, if your values of A, B, and C cause a negative under the square root, you will get a nonreal answer.


    Reply 1 year ago

    This means that the roots of the equation are complex, represented with i. You will learn more about complex numbers in algebra II. For now, the answer to the question "how many roots does this function have" should be no real solutions.


    Question 11 months ago on Introduction

    I cannot find the = sign onmy TI 84+Silver. Thanks Steve


    2 years ago

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


    2 years ago

    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

    Reply 2 years ago

    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.


    2 years ago

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