Solution 27390: Dots or Lines Appearing on a Graph When Using a TI-83 Family, TI-84 Plus Family, or a TI-Nspire™ in TI-84 Plus Mode.
Why does my graph have lines or dots through the display on my TI-83 family, TI-84 Plus family, or TI-Nspire in TI-84 Plus Mode?
After graphing on the TI-83 family, TI-84 Plus family, or TI-Nspire in TI-84 Plus mode a series of dots or lines may appear through the display. The dots represent the graph's grid and when zoomed in to a smaller portion of the graph, can appear as solid lines. This option may be turned on or off by accessing the FORMAT menu.
As an example, graph Y1 = X^2 by doing the following:
• Press [Y=].
• In Y1, press [X] [x²].
• Press [ZOOM] .
• Pressing [ZOOM]  to fit the function properly on the screen.
To turn off the Grid, do the following:
• Press [2ND] [FORMAT].
• Press [↓] [↓].
• Press [ENTER].
• Press [GRAPH].
The dots or lines should no longer be displayed.