This is a difficult set of functions to graph simultaneously given the different families they belong to. The best you can do is to capture the extremes and use the TRACE-function to display the nature of the function that hugs the x-axis.
I looked at the three graphs... the first is a line, the second is a downward facing parabola, and the third resembles a normal distribution graph.
Initially, I used the ZoomStd function which sets the graphing window settings to
X:[-10, 10, 1] Note: [Xmin, Xmax, Xstep]
Y:[-10, 10, 1] [Ymin, Ymax, Ystep]
The line has a y-intercept of -500, so I set the Ymin setting to -600 and the Ystep to 100, i.e., Y:[-600, 10, 100]
Next, I focused on the parabola behavior. To see more of the behavior, I changes the Ymax value to 600, i.e., Y:[-600, 600, 100].
With this setting, I can see the parabola is rising strongly and so we need more x-axis. So, I trippled the right hand edge of the window to 30 and changed the Xstep to 5, i.e., X:[-10, 30, 5]
Using the TRACE function, I enter values of x = 5, 10, 20, 30 and see the values of the parabola are on the order of 1,000-3,000. So, I changes the Ywindow values to i.e., Y:[-600, 4000, 1000].
We see that the parabola still is rising strongly, so I triple the right edge of the Xwindow to 90 with a Xstep of 10, i.e., X:[-10, 90, 10]. The right edge of the parabola is producing values on the order of 8,000 and starting to slow it's rate of rising, so we're going to change the Ymax to 12,000 and the Xmax to 180.
i.e., X:[-10, 180, 50]
. Y:[-600, 12,000, 1000]
It looks like we have the left half of the parabola, so let's double the Xmax = 350 and increase Ymax to 15,000
i.e., X:[-10, 350, 50]
. Y:[-600, 15,000, 1000]
Now, we have nearly the entire parabola, so we're going to adjust the final values to
i.e., X:[-100, 600, 100]
. Y:[-1000, 15,000, 1000]
which captures and displays the line and the parabola. The third function, the graph that looks like the normal distribution, has such a small range that it doesn't display on the graph, but that's unavoidable.
To find the x & y intecepts, maxima and minima would best be done using the TRACE function or the CALC functions accessed using 2nd + TRACE
