If you often find that you enter an equation only to wonder where it went (because none of the curve was on-screen with the current grid range), you may want to try the AutoRange feature. When this checkbox in the Options menu is selected, any time you enter a new Cartesian function of x and more than 20% of the graph's on-screen domain maps to a y-coordinate that is outside of the current range, the program will automatically adjust the y-axis range to show as much as possible of all on-screen curves (see the discussion of the Find All Graphs menu item for an explanation of the process). With the curve no longer hiding out of sight, you may then zoom or scroll as you like to focus on the portion of interest.
AutoRange is off by default. Since it may involve recalculating all graphs when the range is recomputed, it may not be appropriate for slower machines.