Question about Texas Instruments TI-85 Calculator

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Entering y1 in program mode

Hopefully simple question -

i am writing a program to input euler's equation (y=y1*h where h is a change in t for each subsequent y) in the ti-85

i have written my equation under graph as y1=y^2+x^2 (as an example)

i have entered all the steps i need in program mode, except i cannot for the life of me find a way to simply get the characters y1 within the program lines.

Any thoughts? how do i enter y1 in program mode?

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  • bonpatel Jan 28, 2009

    i want to write x+y=98,so how should i do that?



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  • 35 Answers

First, you cant put Y in Y(X)

Hit [2nd] [ALPHA] [0] [1]

Posted on Nov 25, 2008


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Is there a way that I can put in a function and the input, for example the problem h(x)=ax^2+bx+c, and find the function of 0. I have a TI-84 Plus. Can I put this equation in and get it simplified somehow?

If I understand your question correctly, this is what you can do. Go to 'Y='. Put (for example) 3x^2+4x+5 in Y1. Press '2nd', 'Quit' to go back to the home screen. Press 'Vars', arrow right to 'Y-Vars', 'Enter' on 1:Function, and 'Enter' on Y1. This should put Y1 on the home screen. After Y1 type a parenthesis, the number you want to evaluate, and another parenthesis, like this: Y1(7). Press 'Enter'. You should get 180.

Feb 06, 2011 | Texas Instruments TI-84 Plus Calculator

1 Answer

What is the equation of the pair of points (-5,-8) and (-3, -1)

The site seems to eat the plus signs I enter, so I will use PLUS to symbolize addition.

To find the equation of the straight line (
y = a*x PLUS b) that passes through two points P1(x1,y1) and P(x2,y2) , you need to use
1. the coordinates of the points to calculate the slope a (gradient) as a=(y2-y1)/(x2-x1)
Replace the calculated value of a in the equation and write that one of the points ( P1(x1,y1) for example) satisfies the equation. In other words y1=a*x1 PLUS b.
Here y1 and x1 are known values, a has been calculated, and only b is still unknown. You can now use the equation
y1=a*x1 PLUS b to calculate b as

Example: Equation of the line through (1,5) and (3,6)

Calculate the slope (gradient) of the line as a=(y2-y1)/(x2-x1) where y2=6, y1=5, x2=3, and x1=1. You should get a=(6-5)/(3-1)=1/2
The equation is y=(1/2)x PLUS b, where b is not known yet.

To find b, substitute the coordinates of one of the points in the equation. Let us do it for (3,6).

The point (3,6) lies on the line, so 6=(1/2)*3 PLUS b.
Solve for b: 6 MINUS 3/2=b, or b=9/2=4.5
Equation is thus y=(x/2) PLUS 9/2 =(x PLUS 9)/2

I trust you can substitute you own values for (x1,y1, x2,y2) to duplicate the calculations above.

Jan 27, 2011 | Texas Instruments TI-84 Plus Calculator

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When I enter the Regression Equation into the "y=" calculated from the Statistics that I input, it inputs half the equation into the power. Like X^(n 3) instead of X^(n) 3 which is what it is meant to be.

The regression equation can be copied automatically in a Yx variable. You need not enter it manually(?).
Example: Suppose you are performing a quadratic regression on data stored in L1 and L2.
  1. From the [Stat][

Oct 12, 2010 | Texas Instruments TI-84 Plus Silver...

1 Answer

How to program quadratic equation

I have no idea what you mean by program in this context. So I am going to assume you want to solve, because that is what one is supposed to do with an equation.

Suppose you have the quadratic equation a*X^2+b*X+c=0, where a, b, and c are constants. Specify your own constants if you want to use this calculator.

  1. Define a function Y1= a*X^2+b*X+c
  2. Graph it if you want.
  3. Use the solve( command to find the roots of the equation (the zeros of the function)
To access the solve (
  • Press [2nd][0] to open the (CATALOG) of commnands
  • Press [LN] (S) to jump to the first command in the CATALOG that starts with S.
  • From there, scroll down till you point to solve(
  • Press [ENTER]
  • Commnd echoes on main calculator screen as solve( with blinking cursor. You must enter the function Y1 you defined before.
  • Press [VARS], and right arrow to highlight [Y-Vars]
  • Select [1:Function] then [1:Y1]
  • Y1 echoes on main screen, which displays solve (Y1
  • Complete the command by entering a comma, X, a comma, initial guess and ) parentheses.
  • The screen dispays solve ( Y1, X, value_of_initial_guess)
  • Press [ENTER]
  • If your guess is good, you will not wait long to have one solution.
  • To obtain the second one, press [2nd][ENTRY] to recall the last command to the command line solve ( Y1, X, value_of_initial_guess).
  • Use the arrow to modify the value of the initial guess, make sure the ) is still there and press [ENTER].
  • If the guess is good you will get the second solution.
Here is an exemple. Y1 is just X^2+X-14. For the negative root I took the initial guess to be -3, and for the positive root the guess is 2.

How did I get such good guesses? Usually it is trial and error, but I cheated: I drew the function to have an idea about the values of X where the function vanishes.


If that is not what you wanted, post a comment in this thread and we will take it from there. If it did not help you, I am sure it will help others.

Jan 30, 2010 | Texas Instruments TI-84 Plus Calculator

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How do you plot two liner equations on a ti-84?

I use one of the graphing APPS or do through a program. I have a users manual for TI 84 silver Edition that shows you how to archive\ unarchive to run programs here at this site. Usually, I tell people to just forget about the programs and use the simple concepts so, that they could operate their calculator better. But, if you notice in those program are actually more powerful than the programs you get on the web, because I wrote them to be flawless, or I only used programs that I knew would not clash and were very well written. Won't y1=(2/5)x-(11/5) and -3x+8 work?

y1=(2/5)x-(11/5) and -3x+8

Sep 29, 2009 | Texas Instruments TI-89 Calculator

3 Answers

Graphing inverse equations

In parametric mode you are not drawing one function, but two functions X1(T) and Y1(T). If you use the DrawInv( command either on X1(T) or Y1(T) you get a syntax error.
However if you are drawing functions in Funct mode you can draw the inverse of the function that has been graphed.
Here is how you do it.

[2nd][Draw][8: DrawInv] [ENTER]
The command appears on the home screen, and you need to tell it the function it will act on. To do so press
[VARS] --> Y-Vars [1:Function]
and select the function you want, say Y1, if Y1 has already been defined.

DrawInv Y1 [ENTER]
Both Y1 and its inverse will be drawn.

Hope it helps.

Sep 02, 2009 | Texas Instruments TI-84 Plus Silver...

1 Answer

I can't see two graphics simultaneously.I write Y1= (something) and then i write another function Y2= (something). But when I click "enter" in the = sign of the second function, the black spot jumps to the...

To view both graphs, the = signs on both y1 and y2 must be contained in black boxes. If you put your cursor over the = sign on the second equation and hit enter, it turns that graph off and you won't be able to see anything but the equation in y1 line. If there is not black box around the = sign of any equation in any of the lines you have typed an equation into, you will not see the graph.

Aug 12, 2009 | Texas Instruments TI-84 Plus Calculator

3 Answers

My calculator will only graph one graph at a time.

This is simple... Back up all RAM, (press second+, then 2, then 1, press enter to back up something if backed up it will have a star by it) Then clear your RAM (pull out your batteries while the calc is still on or press second+, then 7, then 1)
Hope this helps!

Oct 07, 2008 | Texas Instruments TI-84 Plus Calculator

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Graphing multiply equations

When you go to Y=, you should get a list that says:
etc. You just enter the first equation into the Y1= space then hit ENTER and it will go to Y2=. Enter the second equation there. After you have entered all of your equations, push GRAPH and they should come up in order but they will all appear.

Also, make sure your window is set appropriately so that you are able to see all of the graphs.

Lastly, when you look at your Y= screen, are there funny looking arrows before the Y=? If so, do this:

  • Press [APPS] key
  • Select Transfrm from the menu
  • Press 1:Uninstall

  • Hope one of these are helpful!!


    Feb 18, 2008 | Texas Instruments TI-84 Plus Calculator

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