Chapter 1 Section 0 Example 1 on the TI-86

Note that the TI-86 and the TI-85 have slightly different keys. This page uses the keys associated with the TI-86. The differences are in the "2^nd" functions on some of the keys used here. The TI-85 keys will have the same key-face symbol unless otherwise noted.

The first Example in the text asks us to evaluate

E =

(x – y)(xy + z)

(zy – 2x)

when x=2, y=^–1/2 and z=^–3

On the calculator we can do this by assigning values to variables X, Y, and Z, and then entering the expression to evaluate. The following sequence of screen images and comments trace such steps.

Figure 1

We will start by assigning the value 2 to the variable X. We press

to produce Figure 1. Note that at this point the cursor has changed from its usual solid block,

, to a block with an "A" in it,

. This indicates that the calculator is in alphabetic mode. Now, if we press a key we will get the letter (or special symbol) associated with the key.

Figure 2

We want to store the value 2 into the variable X. Therefore, we want to to press the

key to select the letter X. NOTE: The TI-85 and TI-86 calculators are CASE SENSITIVE. The two names, x and X represent two different variables. Be sure that you are consistent within a problem. The TI-86 and TI-85 require the use of the lowercase "x" for some of the internal processing. However, in a problem such as this, where we are doing all of the processing comamnds, we can choose either variable. We will use the uppercase "X", the one on the "+" key. At this point the screen should appear as in Figure 2.

Figure 3

When we left Figure 2 we had formulated a command to store the value 2 into the variable X. However, we had not asked the calculator to perform that task. We press the

key to get the calculator to actually do the command. The calculator acknowledges that assignment with a 2 on the right side of the next line.

We will continue by storing ^–1/2 into Y via the keys . NOTE: we use the key to change the sign of a value and we use the for subtraction. Do not confuse these two keys. And we assign ^–3 to Z via . This should leave the screen as in Figure 3.

Figure 4

Now, all we need to do is to enter the desired expression, namely

(X – Y)(XY + Z)

(ZY – 2X)

We note that the expression contains the implied multiplication of X and Y (in XY), of Z and Y (in ZY) and of 2 and X (in 2X). The calculators need to be told of the multiplication between the variables (we will have to type X*Y for XY) because a construct such as XY is just a new and different variable name. Therefore, we construct the expression as in Figure 4 via the keys

. We note that when the input line gets too long the calculator merely moves to the next line.

Figure 5

In Figure 5 we have pressed the

to perform the calculation and we see the result, 4, displayed at the right of the screen.