# 1.3 Linear Equations in Two Variables

## Presentation on theme: "1.3 Linear Equations in Two Variables"— Presentation transcript:

1.3 Linear Equations in Two Variables
Slope of a Line Find the slope of the lines passing through… (-2,0) and (3,1) (-1,2) and (2,2) (4,-3) and (4,5)

Point-slope Form of the Equation of a Line
Given a point (x1,y1) and slope m y – y1 = m(x – x1) Ex. Find an equation of the line that passes through the point (1,-2) and has a slope of 3. y – (-2) = 3(x – 1) y + 2 = 3(x – 1) 0 = 3x – y - 5

Summary of Equations of Lines
General Form Ax + By + C = 0 Vertical Line x = a Horizontal Line y = b Slope-intercept y = mx + b Point-slope form y – y1 = m(x – x1) Parallel lines have slopes that are Equal. Perpendicular lines have negative reciprocal slopes.

Ex. Find the equations of the lines that pass
through the point (2,-1) and are a.) parallel to and b.) perpendicular to the line 2x – 3y = 5. First, solve for y and find the slope of the line. a.) m = 2/3 Use point-slope form Mult. each term by 3. 3y + 3 = 2x - 4 0 = 2x – 3y – 7 or

b.) What is our slope? Use point-slope form to start. Then put in general form. Dist. Mult. By 2

Similar presentations