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√ √
-π - 2 2 π
| | | | | | | | | | |
−5 −4 −3 −2 −1 0 1 2 3 4 5
2.1.1 Exercises
Find the absolute value of the following numbers:
1. 12
2. −5
3. −π
√
4. 5
√
5. − 5
6. 0
7. −260
Find two numbers that have the given absolute value:
8. 99
9. 5
10. π
√
11. 7
2.2 Inequalities and signed numbers
The inequality symbols < (less than) and > (greater than) are used to state size comparisons between
numbers. It is intuitively clear that
2 < 5, and 15 > 10
because these are comparisons between nonnegative numbers. Can we make sense of the inequality
symbols when negative numbers are involved? It seems reasonableto say that any negativenumber is
less than 0, and therefore less than any positive number. How do we compare two negative numbers?
For example, is −4 greater or less than −2?
We laid out the number line so that numbers increase as we move to the right, and decrease as we
move to the left. For consistency, we extend that rule to the negative side. The rule of thumb is “left
is less” on the number line.
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