# Math 8 Unit 1-The Number System

### 27 terms by KimBarry Plus

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### WHOLE NUMBER

The Numbers from 0 to +α

### NATURAL NUMBER

The Numbers 1 to +α

Also known as Counting Numbers

### INTEGER

The set of whole numbers and their opposites
From -α to +α

### RATIONAL NUMBER

A number that can be written as a/b where a and b are integers, but b is not equal to 0. .25=¼

### IRRATIONAL NUMBER

A number whose decimal form is non-terminating and non-repeating. Cannot be written in the form a/b, where a and b are integers (b cannot be zero).

### REAL NUMBER

The set of all rational and irrational numbers.

### DECIMAL

A number that is written using the base-ten place value system. 5.6

### DECIMAL EXPANSION

Representing a number in decimal form.
¾=.75

### REPEATING DECIMAL

A number whose decimal representation eventually repeats the same sequence of digits. 1/3=.3333333...

### NON-TERMINATING DECIMAL

A decimal numeral that does not end in an infinite sequence of zeros. 1.42345426343517189191........

### TERMINATING DECIMAL

Has a decimal expansion that ends in zero. 0.726500000 = 0.7265

### RATIO

A comparison of two quantities by division.
½ or 1 to 2 or 1:2

### APPROXIMATION

A result that is not necessarily exact, but is within the limits of accuracy required for a given purpose.
146 ≈ 150 2.57≈3

### GREATER THAN

When a number is larger than the other number.
65 > 56

### LESS THAN

When a number is smaller than the other number. 107 < 215

The symbol √ which is used to respresent the square root

### SQUARE ROOT

A number that when multiplied by itself, equals the given number.

### CUBE ROOT

A number that when multiplied by itself, and then mulitplied by itself again equals the given number.

### CUBED

A number cubed is the number raised to the third power.

### PERFECT SQUARE

A number with integers as its square roots.
1,4,9,16,25....

### PERFECT CUBE

A number that can be written as the cube of an integer. 1,8,27,64....

### PYTHAGOREAN THEOREM

In any right triangle, the sum of the squares of the lengths of the legs is equal to the square of the length of the hypotenuse, a²+b²=c²

### CONVERSE

If the square of one side of a triangle is equal to the sum of the squares of the other two sides, then the triangle is a right triangle.

### PROOF

a²+b²=c² where c is the hypotenuse while a and b are the legs of the triangle.

### LEGS

The two sides of a right triangle that form the right angle. ( called a and b)

### HYPOTENUSE

The side of the right triangle that is opposite the right angle ( called c)

### COUNTER EXAMPLE

An example that shows a conjecture is false.

Example: