# Math Midterm

### 18 terms by susnmoon

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### Natural numbers

These are used to count with (starts with 1 to infinity)

### Whole numbers

These numbers are the natural numbers and zero

### Integers

These are the natural numbers, their opposites, and zero

### Rational Numbers

These are all the numbers that can be expressed in a fraction form where m and n are integers and the bottom denominator is not 0. These numbers, when expressed as decimals, end or repeat (includes repeating decimals and fractions)

### Irrational Numbers

These are all the non-terminating numbers and non-repeating decimals (includes pi)

### Real Numbers

These are all rational and irrational numbers (every number you know of)

### Imaginary Numbers

These are numbers that result from a negative number under a square root sign

### Complex Numbers

These are all real and imaginary numbers. It is written of the form a + bi, where "a" is a real number and "bi" is an imaginary part.

### Commutative property

(order): a + b = b + a ORRRR ab = ba

### Associative property

(grouping): (a + b) + c = a + (b + c) ORRRR (ab)c = a(bc)

### Identity property

a + 0 = a, 0 + a = a (additive identiy) ORRRR a x 1 = a, 1 x a = 1 (multiplicative identity)

### Inverse property

a + (-a) = 0 ORRRR a x 1/a = 1

### How do you multiply matrices?

You multiply ROW by COLUMN (The train falls over the cliff)

### How do you determine the determinant?

In 2 x 2 matrices: ad - bc ... . . . . ... In 3 x 3 matrices: Find the minor

### How does the sign array matrix go?

+ - + (top row), - + - (middle row, + - + (bottom row)

### What is the rule for multiplying matrices?

The number of columns in the first matrix MUST EQUAL the number of rows in the second matrix.

### Interval Notation

This is used to represent the interval between two real numbers.

Example: