Write an equation of a line by using the slope and a point on the line.

Point-Slope Form  Uses one point, (x 1, y 1 ) on a line to create an equation

Writing an Equation

Graphing

Standard Form of a Linear Equation  So far we have learned how to write linear equations in slope-intercept form and point-slope form.  Standard form is written Ax + By = C where A, B, and C are real numbers

Intercepts  The x-intercept is the x-coordinate of a point where a graph crosses the x-axis. Found where the y-value is 0  Find x and y intercepts of the graph of 3x + 4y = 24  Sub 0 for y to find x-intercept X =8  Sub 0 for x to find y-intercept Y = 6

Graphing Using Intercepts  What is the graph of x – 2y = -2?  Find intercepts X = -2 Y = 1  Write as ordered pairs (-2, 0) (0, 1)  Plot the ordered pairs

Horizontal and Vertical Lines  x = 3  Write in standard form: 1x + 0y = 3  y = 3  Standard form: 0x + 1y = 3

Transforming to Standard Form

Parallel Lines  Lines in the same plane that never intersect.  Nonvertical lines are parallel if they have the same slope and different y-intercepts.  Vertical lines are parallel if they have different x-intercepts.  Ex: Same slope, different y-intercept

Perpendicular lines