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Evaluating Functions

Functions can be evaluated on the graphing calculator by
the use of functional notation or by graphing.

1.
Evaluating functions using functional notation. 
 
   If f (x) = 3x3 + 2x - 5,  find  f (23.6).  Round to 3 decimal places, if needed.
1
Enter the function in Y=.
2
Go to the home screen.  Using a functional notation format, enter Y1(23.6).  [To get Y1, go to VARS, arrow right to Y-VARS, #1Function, #1Y1.]
3
Hit ENTER.

Answer:  39,474.968

Examples: 

  Function: Evaluate: Answer
(round to 3 decimal places if needed)

1.

 4 5
6
Answer:  -1.337
2.
 7 8
Set MODE to Radian.
9
Answer:  1.913
3.
 10 11
12
Answer:  3.196


 

 

 

2.
Evaluating functions by graphing.

 

 

  
  If f (x) = 3x3 + 2x - 5,  find  f (23.6).  Round to 3 decimal places, if needed.
Step 1: Step 2: Step 3:

13
Enter the function in Y=.

14
Adjust the WINDOW so that the point 23.6 will be shown on the x-axis.

15
Graph

Step 4: Step 5: Step 6:

16
Hit TRACE.  Type 23.6 right on the screen.  It will automatically appear at the bottom of the graph.

17
Hit ENTER.
The answer (the y-value) will appear.

Answer:  39,474.068