Module 1  Describing Functions  
Introduction  Lesson 1  Lesson 2  Lesson 3  Lesson 4  SelfTest  
Lesson 1.3: Describing Functions Graphically  
In Lesson 1.2 you defined the function f(x) = 2x^{2} – 5x – 3 and found its roots symbolically. In this lesson you will display this function graphically and use the graph to find its roots. Recalling a Defined Function Even if you turned off your calculator after completing Lesson 1.2, the function f(x) should still be defined. Verify this by clearing the Home screen and the Edit Line and then entering f(x) on the Edit Line. Click here to see the keystroke sequence to do this. Graphing a Defined Function To graph a function you need to place it in the Y= Editor. The Y= feature is found above the key. You will now define y1= f(x) , set the viewing window, and graph the function
Entering a Defined Function into the Y= Editor Make sure y1 is clear and the cursor is by y1.
As you press the keys, the expression is displayed in the Edit Line. When you press , the function appears by y1. Setting the Viewing Window
Before you graph the function, you need to specify the
The values of the parameters of the Viewing Window determine the size of the window in which the graph appears.
The window values shown above are appropriate for our function's graph, so we will keep them. If you need to change your window values to match those shown above, you can do this by moving the cursor to the appropriate line with the cursor movement keys and then entering the desired values. Displaying a Graph Display the graph when the window values are correct.
Finding Roots Graphically You can find the roots of the function from the graph screen.
You will see the graph and a prompt for a lower bound, as shown at right below.
After you press , a small marker appears at the top of the graph above the lower bound, as shown at the top of the graph at right below. The calculator then asks you to indicate an upper bound.
The root is x = 3. 1.3.1 Use the Math Zero feature to find the other root. Click here for the answer. 

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