Answer Key - St. Louis Public Schools



Reteach

Sets of Numbers

As you move from left to right on a number line, the numbers increase.

Use a number line to help you order real numbers.

Order from least to greatest:

[pic]

Use a calculator to approximate [pic] and [pic] as decimals:

[pic] ≈ 3.32 and [pic] ≈ −1.57.

Plot each point on a number line.

[pic]

Read the numbers from left to right on the number line.

From least to greatest, the order is [pic]

Order the given numbers from least to greatest. Use a number line to help you.

1. π, [pic], [pic], −0.456, and [pic]

π ≈ 3.14, [pic] ≈ 2.67, and [pic] ≈ 1.73 [pic]

2. −1.75, 1, [pic], 1.55, and [pic]

[pic] ( ____________ [pic]

[pic] ≈ ____________

3. [pic] and [pic]

[pic] ≈ ____________ [pic]

[pic] ≈ ____________

[pic] ≈ ____________

Reteach

Sets of Numbers (continued)

You can represent the same set in different ways.

Number line: [pic]

Words: The set of numbers greater than or equal to −2 and less than 0

OR greater than or equal to 1

Interval Notation: [−2, 0) or [1, ∞)

Set-Builder Notation: {x ( −2 ≤ x < 0 or x ≥ 1}

This set cannot be described in roster notation because you cannot list

the real numbers in the intervals shown on the number line.

The roster notation of [pic], the set of natural numbers, is {1, 2, 3, ...}.

The set-builder notation of [pic] is {x(x ( [pic]}.

Rewrite each set using the indicated notation.

4. the set of integers, or [pic]; roster notation {…, −3, −2,_______________________________}

5. {0, 4, 8, 12, 16, …}; words

6. −5 ≤ x ≤ 12; interval notation [ _______________________________

7. {x(x < 0}; interval notation (−∞ _______________________________

8.

set-builder notation {x( _______________________________

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LESSON

1-1

LESSON

1-1

( means infinity and

–( means negative infinity.

Brackets [ ] include the endpoints.

Parentheses ( ) do not include endpoints.

Read this as “x such that”

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