Point-Slope Form Linear Equations in Two Variables

What we Know so far…. Slope Intercept Form Where m is the slope and b is the intercept

The New Stuff… Point- Slope Form Point- Slope form is: Where m is the slope and (x 1, y 1 ) is the given point

Write the Equation in Point-Slope Form Step 1: Plug it in Point- Slope Form Slope – Intercept Form

5 A linear equation written in the form y – y 1 = m(x – x 1 ) is in point-slope form. The graph of this equation is a line with slope m passing through the point (x 1, y 1 ). Example: The graph of the equation y – 3 = - (x – 4) is a line of slope m = - passing through the point (4, 3) (4, 3) m = x y Plot the point, then rise & run from there….

Using Point-Slope Form (2,2) We need the slope and a point: Plug them into the point-slope form Point – Slope Form

7 Example: Write the point-slope form for the equation of the line through the point (-2, 5) with a slope of 3. Use the point-slope form, y – y 1 = m(x – x 1 ), with m = 3 and (x 1, y 1 ) = (-2, 5). y – y 1 = m(x – x 1 ) y – 5 = 3(x – (-2)) Let m = 3, let (x 1, y 1 ) = (-2, 5). y – 5 = 3(x + 2) Simplify into point-slope form

Given two points, write the equation of a line in point-slope form Steps: 1. Find slope2. Place a point and the slope in into point slope form 3. Point-Slope form (2,-3) and (4,-2) Slope-intercept form Solve for y & get..

Simplify using distributive property, then move the constant to the right side & combine like terms To write point-slope into slope-intercept:

10 Example: Write the slope-intercept form for the equation of the line through the points (4, 3) and (-2, 5). y – y 1 = m(x – x 1 ) Point-slope form Slope-intercept form y = - x – 3 -2 – 4 = Calculate the slope. m = Use m = - and the point (4, 3). y – 3 = - (x – 4) 1 3 Solve for y…

A Challenge Can you write the equation of a line in point-slope form that passes through (-3,6) and (1,-2) – 1 = Calculate the slope. m = y – y 1 = m(x – x 1 ) y + 2 = - 2 (x – 1) Use m = - 2 and the point (1, -2). y = -2(x – 1) - 2 y = -2x y = -2x + 0y = -2x Point-Slope Form Slope-Intercept Form