You can use the TI-84 Plus calculator to find accurate points of intersection for two graphs. Using the arrow keys in a graph activates a free-moving trace. However, using a free-moving trace rarely locates the point of intersection of two graphs but instead gives you an approximation of that point.
To accurately find the coordinates of the point where two functions intersect, perform the following steps:
Graph the functions in a viewing window that contains the point of intersection of the functions.
Press [2nd][TRACE] to access the Calculate menu.
Press [5] to select the intersect option.
Select the first function.
If the name of one of the intersecting functions does not appear in the border at the top of the screen, repeatedly press the up- and down-arrow keys until it does. This is illustrated in the first screen. When the cursor is on one of the intersecting functions, press [ENTER] to select it.
Select the second function.
If the calculator does not automatically display the name of the second intersecting function in the border at the top of the screen, repeatedly press the up- and down-arrow keys until it does. This is illustrated in the second screen. When the cursor is on the second intersecting function, press [ENTER] to select it.
Use the right- and left-arrow keys to move the cursor as close to the point of intersection as possible.
This is illustrated in the third screen.
Press [ENTER] to display the coordinates of the point of intersection.
If there are only two functions in the Y= editor, you can save time by pressing [2nd][TRACE][ENTER][ENTER] to choose your functions. If there is only one point of intersection of the two functions, then press [ENTER] again to calculate the point of intersection. It is only necessary to make a guess when there is more than one point of intersection.