Quick Graphing Using Slope Intercept Form What are

Quick Graphing Using Slope -Intercept Form

What are the different methods we have used to graph a line? • Plot points • Make a table • Find the x and y- intercepts • Special horizontal and vertical lines

Slope-intercept form: linear equation y = mx+b m represents the slope of the line b represents the y-intercept *where the line crosses the yaxis

y = mx + b You can tell by looking at the equation not only where the line crosses y, but whether it has a positive or negative slope. If m is positive the slope is positive, and your line will go up from left to right. If m is negative, the slope is negative and your line will go down

Determine what is the slope, y-intercept, and direction of each equation. 1. y = 3 x + 4 2. y = ½ x – 9 3. y = -4/5 x + 7 4. y = -2 x - 4 1. Slope = 3 y-intercept = 4 goes up left to right 2. Slope = ½ y-intercept = -9 goes up left to right 3. Slope = -4/5 y-intercept = 7 goes down left to right 4. Slope = -2 y-intercept = -4 goes down left to right

When your equation is not in slope intercept form, rewrite it into slope-intercept form (y=mx+b). 2 x = 5 y - 10 • 2 x = 5 y-10 -5 y • 2 x – 5 y = -10 -2 x • -5 y = -2 x – 10 -5 -5 -5 • y = 2/5 x + 2 What is the y- intercept? What is the slope? What direction will the line go? 2/ 2 5 Up, from left to right.

Graph the line y = 2/ 5 x +2 The slope is 2/5 & the y-intercept is 2. Steps to graphing a line in slope intercept form: 1. Plot the yintercept. (0, 2) 2. Count up 2 over 5 and plot next point. 3. Connect the dots. 4 3 2 1 -4 -3 -2 -1 -1 1 2 3 4 5 6 -2 -3 -4

Graph the line 2 y = -2 x + 6 1. Change to slope intercept form. 4 3 2. y = -x + 3 2 3. Y-intercept (0, 3) 1 4. Slope -1 -4 -3 -2 -1 -1 1 2 3 4 5 6 5. Line will go down -2 from left to right. -3 -4

Special line: • Parallel Lines: lines have the same slope, but different yintercept (b value) • y = 2 x + 4 and y = 2 x – 3 are parallel lines.

Graph y = -x+6 and y = -x+2 on the same graph. Notice that they each have the same slope of -1, but they cross y at different spots.