Slope – Intercept Form

Objective: Students will investigate graphs to determine what the coefficients and constants represent in the slope-intercept form equation. Students will create equations in slope-intercept form given the slope and the y-intercept. Students will be able to graph linear equations given in slope-intercept form using only the slope and the y-intercept.

ACTIVITY! QUICKLY get into a group of 2 or 3. One person needs to record thoughts from the group members and one person needs to make sure that the group stays on task.

Look at these two graphs closely, what observations can you make relating the graph to the formula? y = x + 2y = - x –

Let’s Discuss! What are your thoughts about the graphs and how they relate to their formulas? Given the following formula, what can you tell me about each letter? (Use mathematical terms!!) y = mx + b slope–intercept form

Write an Equation! Write an equation in slope-intercept form given the slope of 3 and a y – intercept of 7 y = 3x + 7 Write an equation in slope-intercept form given the slope of -2 and a y – intercept of -1 y = -2x -1

Your Turn! Write an equation in slope-intercept form given the slope of ½ and a y – intercept of 4 y = ½ x + 4 Write an equation in slope-intercept form given the slope of ⅗ and a y – intercept of -5 y = ⅗x – 5

Let’s go the other way… Given the following linear equation, determine the slope and the y – intercept. y = ⅔x + 5 m = ⅔ y – intercept = 5 y = -3x m = -3 y – intercept = 0 -3x + y = 8 OH NO!! WHAT FORM IS THIS IN?! WHAT FORM SHOULD IT BE IN?! y = 3x + 8 m = 3 y – intercept = 8

Your Turn! Given the following linear equation, determine the slope and the y – intercept. 1) y = 4x + 7 m = 4 y – intercept = 7 2) 2x + y = -4 y = -2x – 4 (change from standard form to slope-intercept form!) m = -2 y – intercept = -4

Let’s Graph! Use only the slope and y-intercept to graph the equation. y = -x + 5 3x + y = 9