How do you program TI-83 calculator to input variable values to solve or calculate an equation?

Answer 1

Variables on the TI-84 Plus Silver hold numbers; there are like memory. Here is an example of how to wet the variable C to equal 24:

Enter the number 24, then press the STO> key. Then press ALPHA C (above PRGM). The calculator should show:

24->C

Press ENTER and the variable C will be set to 24. You can check this by pressing ALPHA C and then ENTER.

Answer 2

To start a program, press PRGM and then NEW and make a program. To input values from the user, use Prompt (press PRGM and then I/O at the top.) These values will be stored in the letter variables on your calculator Use Disp (press PRGM and then I/O at the top) to display values to the user. For example, to ask the user for the values of A, B, and C and then display the value of AB2 - C, use this program:

:Prompt A,B,C

:Disp AB2 - C

The calculator can solve an equation with one variable. Doing so in a program gets kind of complex. You use solve to solve an equation (while editing a program, press MATH and look at the bottom of the list.) To use solve, give it an expression (which will be set equal to 0 and solved by the calculator as an equation, a variable (to tell the calculator what to solve for), and a guess (the calculator will find a number close to this guess. It only finds one number at a time, even if there is more than one solution.)

To ask the user for both sides of an equation, you will have to store these as strings. You will have to use Input, not Prompt, to ask the user for these strings. (Get to Input by pressing PRGM and then I/O at the top. Get to the strings by pressing VARS and then String...) When using input, you can tell the user what you want in quotes, then a comma, then where to store the data. For example, to ask the user for the left side of the equatino and store that to string 1, use this line of code:

:Input "LEFT:",Str1

Your strings will then need to be converted into equations. Use String>Equ to do this. (Press 2ND CATALOG (above 0), then 4 (to go to the letter t's) and then scroll up to find it.) Press VARS, then Y-VARS at the top, then Function... to get to the functions. For example, to convert string 1 into the function Y1:

:String>Equ(Str1,Y1)

Finally subtract the two equations from each other, which will be set equal to 0, and solve using the solve function. Here is a program that will solve for the variable X. (X must be used as the varaible. Any other letter will not work.) G is a guess input by the user so that the user can change which solution (if there is more than one) is found each time they run the program:

:Input "LEFT",Str1

:Input "RIGHT",Str2

:Prompt G

:String>Equ(Str1,Y1)

:String>Equ(Str1,Y2)

:Disp solve(Y1-Y2,X,G)

If you have a set equation you want to solve for where you know the values of all but one variable, you could do this:

(In this example the equation is A+B = CX, where X is unknown. G is still a user guess. Note that this is the same as A + B - CX = 0.)

:Prompt A,B,C,G

:Disp solve(A+B-CX,X,G)