Equations of Lines in the Coordinate Plane The slope m of a line is the ratio `of the vertical change (rise) to the horizontal change (run) between any two points.

Find Slopes of Lines Find the slope of line a and line d.

Slopes of Lines in Coordinate Planes Negative slope – falls from left to right. Positive slope – rises from left to right. Zero slope (slope of 0) – horizontal line Undefined slope – vertical line

Forms of Linear Equations The slope intercept form of an equation of a nonvertical line is y = mx + b, where m is the slope and b is the y-intercept. The point-slope form of an equation of a nonvertical line is y – y1 = m (x – x1), where m is the slope and (x1 , y1) is a point on the line.

Graphing Lines What is the graph of Starting point (0 , 1)

Graphing Lines What is the graph of y – 3 = -2 (x + 3) Starting point (-3 , 3)

Writing Equations of Lines What is an equation of the line with the slope 3 and y – intercept -5? y = mx + b y = 3x – 5

Writing Equations of Lines What is the equation of the line through point (-1 , 5) with slope 2? y – y1 = m (x – x1)

Using Two Points to Write an Equation What is an equation of the line with points (-2 , -1) and (3 , 5)?

Writing Equations of Horizontal and Vertical Lines What are the equations for the horizontal and vertical lines through (2 , 4)? y = 4 – horizontal line x = 2 – vertical line