Algebra (Period 1)

The Number Systems Section 2-2

Natural (counting): 1, 2, 3, ....

Whole: 0, 1, 2, 3, ...

Integers: ...-3, -2, -1, 0, 1, 2, 3, ...

Rational: All numbers that can be written as a fraction or RATIO (decimals-terminating and repeating, fractions, mixed numbers, integers)

Irrational: Decimals that never terminate or repeat - like pi and square root of 2


Real numbers: All the number systems together


Complex or Imaginary Numbers: we don't study these until Algebra II, but they are stated as "
a + bi" where i is equal to the square root of -1



DENSITY PROPERTY: Between any 2 rational numbers is another rational number

Rational number = any number that can be expressed as the ratio (fraction) of two integers
a/b, where a and b are both integers and b cannot be zero
.
"b" cannot be zero because you cannot divide by zero.....IT'S UNDEFINED!

There are positive and negative rational numbers.

One way to put them in order from least to greatest is to simply place them on the REAL number line.
Numbers will be least to greatest if read from the left to the right.

If you have both fractions and decimals, it's often easier to change the fractions into decimals by simply dividing the numerator by the denominator.

REMEMBER: When numbers are NEGATIVE, the closer they are to zero, the bigger they are.
Example: -1/2 is greater than -3/4
-2.3 is greater than -2.5