To graph an equation on a TI-84 Plus, you press the Y= button, type your equation, and press GRAPH. That’s the core sequence, and it works for everything from simple lines to complex polynomials. But getting a useful, readable graph usually involves a few more steps, like adjusting your viewing window and using built-in tools to find key points. Here’s how to do all of it.
Entering Your Equation
Press the Y= button in the top-left corner of the calculator. This opens the equation editor, where you’ll see a list of slots labeled Y1=, Y2=, Y3=, and so on. Each slot holds one equation, and the calculator can graph all of them simultaneously.
Place your cursor next to Y1= and type your equation. Use the X,T,θ,n button (located just below the screen on most models) to enter the variable X. So for the equation y = 2x + 3, you’d press 2, then X,T,θ,n, then +, then 3. For exponents, use the ^ key. To graph y = x², press X,T,θ,n, then ^, then 2.
If old equations are cluttering the screen, move the cursor onto each one and press CLEAR to delete it. You can enter equations in multiple Y= slots to graph several functions at once, which is useful for finding where two curves intersect.
Turning Off Stat Plots
Before you graph, check the top line of the Y= screen. If you see Plot1, Plot2, or Plot3 highlighted, a stat plot is active. This is one of the most common reasons a graph looks wrong or throws an error. Move your cursor up to the highlighted plot name and press ENTER to deactivate it. Alternatively, press 2nd then Y= (which opens STAT PLOT), and select 4:PlotsOff to turn them all off at once.
Displaying the Graph
Once your equation is entered, press the GRAPH button in the top-right corner. The calculator draws your function on the coordinate plane. If you’ve entered equations in multiple Y= slots, all of them appear on the same screen, each drawn as a separate curve.
If nothing appears on the screen, don’t panic. Your equation might be graphed outside the visible area. The default viewing window only shows x-values and y-values between -10 and 10. If your function produces values outside that range (or only has interesting behavior far from the origin), you’ll need to adjust the window.
Adjusting the Viewing Window
You have two ways to control what portion of the coordinate plane is visible: the ZOOM menu for quick presets, and the WINDOW button for manual control.
Using Zoom Presets
Press the ZOOM button to see a list of preset viewing options. The most useful ones are:
- 6:ZStandard resets the window to the default, with x and y both running from -10 to 10 and the origin centered on screen. This is a good starting point when your graph looks off.
- 0:ZoomFit keeps your current x-range but automatically adjusts the y-range so the entire curve is visible. Helpful when you can see part of your graph but it runs off the top or bottom.
- 9:ZoomStat adjusts the window to fit any statistical data you’ve entered in lists. Use this when you’re graphing stat plots rather than equations.
Select any zoom option by scrolling to it and pressing ENTER. You can also press ZOOM and then just type the number (for example, ZOOM then 6 for ZStandard).
Setting the Window Manually
For precise control, press the WINDOW button. You’ll see several settings you can edit directly:
- Xmin and Xmax set the left and right boundaries of the screen.
- Ymin and Ymax set the bottom and top boundaries.
- Xscl and Yscl control the spacing of tick marks on each axis. Setting Xscl to 5 places a tick mark every 5 units along the x-axis.
Type new values for any of these and press ENTER to confirm each one. Then press GRAPH to see the updated view. If you’re graphing y = x³ and want to see its behavior from -20 to 20, set Xmin to -20, Xmax to 20, Ymin to -8000, and Ymax to 8000.
Tracing Along the Curve
Press the TRACE button to place a cursor directly on the graph. As you press the left and right arrow keys, the cursor moves along the curve and the screen displays the x and y coordinates at each point. This is a quick way to read approximate values off the graph.
If you have multiple equations graphed, press the up or down arrow keys while in TRACE mode to jump between curves. The equation currently being traced appears at the top of the screen.
You can also type a specific x-value while tracing. Just press a number (say, 5) and then ENTER. The cursor jumps to that x-value on the curve and shows you the corresponding y-value. This is faster than scrolling with the arrow keys when you need a particular point.
Finding Zeros, Intersections, and Extremes
The CALC menu gives you precise answers for key features of your graph. Access it by pressing 2nd and then TRACE (the word CALC is printed above the TRACE key).
Finding Zeros (X-Intercepts)
Select 2:zero from the CALC menu. The calculator asks three questions in sequence:
- Left Bound? Move the cursor to the left of where the curve crosses the x-axis and press ENTER.
- Right Bound? Move the cursor to the right of that crossing and press ENTER.
- Guess? Move the cursor close to the crossing point and press ENTER.
The calculator then displays the exact x-value where the function equals zero. If your equation crosses the x-axis in multiple places, repeat the process for each crossing.
Finding Intersections
To find where two graphed equations cross, select 5:intersect from the CALC menu. The calculator asks you to confirm the first curve (press ENTER), confirm the second curve (press ENTER), then move near the intersection point and press ENTER for your guess. It returns the exact coordinates where the two functions meet.
Finding Maximums and Minimums
Select 3:minimum or 4:maximum from the CALC menu. The process works the same as finding zeros: set a left bound, a right bound, and a guess. The calculator returns the x and y coordinates of the highest or lowest point within that interval. This is especially useful for parabolas and other curves with turning points.
Graphing in Parametric and Polar Modes
The TI-84 Plus isn’t limited to standard y = f(x) graphs. Press the MODE button to see the graphing mode options in the fourth row of the screen: Func (function), Par (parametric), Pol (polar), and Seq (sequence). Highlight the one you want and press ENTER.
In Parametric mode, the Y= editor changes to accept paired equations. Instead of Y1, you’ll see X1T and Y1T, where both x and y are defined as functions of a parameter T. Enter one equation for X1T and another for Y1T. Press WINDOW to set Tmin, Tmax, and Tstep (how finely the calculator plots along the parameter range), then press GRAPH.
In Polar mode, the editor displays r1 through r6, and you enter equations in the form r = f(θ). The WINDOW settings include θmin, θmax, and θstep. For a full rotation, set θmin to 0 and θmax to 2π (type 2, then 2nd, then π).
When you’re done with parametric or polar graphing, remember to switch back to Func mode. Otherwise, the calculator will expect parametric or polar input the next time you try to graph a standard equation.
Fixing Common Graphing Problems
If you press GRAPH and see an “ERR:INVALID DIMENSION” message, a stat plot is almost always the cause. The calculator is trying to reference a data list that doesn’t exist. Press 2nd then Y= and select 4:PlotsOff to clear all stat plots, then try graphing again.
If the screen is blank after pressing GRAPH, your function is probably outside the visible window. Press ZOOM and select 6:ZStandard to reset to the default view. If the graph still doesn’t appear, try 0:ZoomFit to let the calculator auto-scale the y-axis.
If the graph looks like a strange zigzag or has unexpected vertical lines, you may be seeing the calculator connect points across a discontinuity (like a vertical asymptote). Press MODE, scroll to the option that says “Connected” or “Dot,” highlight Dot, and press ENTER. This plots individual points without connecting them, which gives a cleaner picture for functions with asymptotes or jumps.
If your equation uses negative numbers, make sure you’re using the correct minus sign. The (-) key at the bottom of the keypad is for negative signs. The subtraction key (the minus on the right side) is for subtraction. Mixing these up produces a syntax error.