Technology objective: Students should be able to enter integers into both the TI-34 and the TI-81 calculators as well as use the absolute value key.
Lesson: After an introduction to integers, students are going to be curious how to enter those integers on their calculators. This is a good time to reinforce the terminology.
To enter -3, you must enter the number, 3, followed by the "+/-" key. If you press the "+/-" key again, the negative sign goes away. Press the "+/-" key again the negative sign comes back. (This can be good to know if you make a mistake and want to fix it right away.)
To enter -3 in the TI-81, you need to enter the negative sign first, just as it appears. The negative sign looks like this: (-). Students have a tendency to enter minus three instead of negative three.
For example, have the students enter the following problem: 1 - -3
This is read as 1 minus negative three so they will need to type it in as so. If they type in 1 minus minus three an error message will appear.
Students should be reminded that absolute value is the distance a number is from the zero point on the number line. To find the absolute value of a number, you will have to use the ABS key - this is written in blue above the x inverse key. To access this key you will have to press the 2ND key first.
To find the absolute value of a number in the TI-81 calculator:
1. Press the 2ND key.
2. Press the ABS key. The word ABS comes up on the screen of your calculator.
3. Now enter the number you want to find the absolute value of.
Have the students find the absolute value of the following on their own, then check their work using the TI-81 calculator.