A TI-84 Plus calculator cannot find the domain and range of a function directly, but it can help you graph the function and estimate its domain and range. Here are the steps you can follow:
1. Press the "Y=" button to enter the function you want to graph.
2. Use the arrow keys to navigate to the line of the function you want to edit.
3. Use the "CLEAR" button to delete any existing function.
4. Enter the new function using the variables "X" and "Y".
5. Press the "GRAPH" button to graph the function.
6. Use the "ZOOM" button to adjust the viewing window if necessary.
7. Estimate the domain and range of the function by looking at the x-axis and y-axis values that are visible on the graph.
Note that this method only provides an estimate of the domain and range, and it may not be accurate for all functions. To find the exact domain and range of a function, you may need to use algebraic methods or consult a textbook or other reference material.