## 1. THE DISTANCE FORMULA

### 1.1. it is used to find the distance between two points on the coordinate plane

### 1.2. Pythagorean Theorem can be used to find the distance between two points.

## 2. MIDPOINT FORMULA

### 2.1. the midpoint of a segment is a point that divides the segment into two congruent segments

### 2.2. to find the midpoint of a line, simply find the x and y coordinates of the midpoint

## 3. WRITING THE EQUATIONS OF THE LINE

### 3.1. linear equations can be written in 3 forms

3.1.1. Standard Form : Ax + By = C

3.1.2. General Form : Ax + By + C = 0

3.1.3. Slope - Intercept Form : y = mx + b

## 4. GRAPHING LINEAR EQUATIONS

### 4.1. we can graph linear equations using

4.1.1. x - and y intercepts

4.1.2. a point and slope of the line

4.1.3. two points of the line

## 5. PARALLEL AND PERPENDICULAR LINES

### 5.1. Two lines are parallel if they have the same slope and different y - intercepts

5.1.1. slope of L1 = slope L2

### 5.2. Two lines are perpendicular if their slopes are opposite reciprocals

5.2.1. the product of their slopes is always equal to -1