By using the 2nd function
feature of the
key you can have your calculator find or calculate many values of interest.
When you press
you see the CALCULATE menu shown below.
Option 1 allows you to type in an x–value and have the calculator give you the corresponding y-value. However, there is a quicker way to accomplish this with fewer keystrokes.
Suppose you have y = 2x2
+ 6x - 1 and the following graph
of the function.
Now, what if you want to find out the y–value when x = 4? Press
and then press
When you press
you will see the y–value at the bottom of the screen.
When using this option, the x–value must be in your viewing window, otherwise the calculator will display an error message. If you need help setting your window, click here
So, when using the CALCULATE menu, you really do not need option 1. It just requires more keystrokes than the method shown here. However, the other options from this menu are extremely useful.
Option 2 allows you to find the zeros of a function. You may have also heard these referred to as roots or x – intercepts. No matter
what you call it, this is where the graph
touches the x – axis.
Let y = x2
+ x - 6 . By using factoring methods (this should link to Donna’s lesson on factoring trinomials) you can discover that the zeros are a x = 2 and x = -3. How can we use the calculator to come up with those same values?
To see the same screens shown below, graph
y1 in a standard viewing window. You can get help with graphing
if you need it.
and you should see
By using this option, you have asked the calculator to find a zero for you. The calculator is now asking you to narrow its search. It begins by asking you for a Left Bound. Simply move your cursor with the arrow keys somewhere to the left of the zero. Since you’re pretty sure one zero occurs at x = -3, move the cursor to the left (or less than) that value. You will see ugly values at the bottom of your screen as you move the cursor. Don’t worry about this. Remember this can be avoided by using a friendly window, but it is not a concern for us during this lesson. The only important thing is to find a place to the left of the zero and press
The calculator now wants a Right Bound. Use the
to position the cursor to the right of the zero and press
. You are now being asked for a Guess. You just have to press
and the calculator will give you an answer.
This only gave you one of the zeros. You have to repeat the process to find the other zero of x = 2. Make sure you can do that here.