Vanessa E. answered • 05/26/13

Effective Math Instructor with 10+ of Teaching Experience

Hi Kristine! My name is Vanessa and I can help you plot the line of y = 3x - 1.

In order to do this you need to follow these five (5) steps:

1) **Know what each of the variables mean in an equation of a line.** The equation of a line is y = mx + b where y = y-coordinate, m = slope, x = x-coordinate, and b = y-intercept. (Remember that the slope is the *steepness* of a line and the y-intercept is the point where the line *intersects * the y-axis. The x- and y-coordinates are values of the points on the line of y = 3x - 1.)

2) **Identify the m (slope) and the b (y-intercept)**. The slope is 3, which can also be written as 3/1. The y-intercept is -1. (Remember that subtraction of 1 is the SAME thing as adding -1!) Since the y-intercept is a point it will be plotted at (0, -1).

3) **Plot the y-intercept first.** Start at the origin (intersection of the x- and y-axes) since the x coordinate is 0. Then move DOWN 1 unit since the y-coordinate is negative.

4) **Use the m (slope) to plot at least three new points.** The slope can also be represented as "rise/run" or the amount of units that you move UP or DOWN (vertically), *then* LEFT or RIGHT (horizontally). (Remember: if the numerator is positive (move UP); numerator is negative (move DOWN); denominator is POSITIVE (move RIGHT); denominator is NEGATIVE (move LEFT)). Since our slope is 3/1, and both the numerator and denominator are POSITIVE, that means we will be "rising" (moving UP) 3 units and "running" (moving RIGHT) 1 unit.

Start at the y-intercept* * of (0, -1) and move up 3 units and to the right 1 unit. You should be at (1, 2). Plot a point here. Then do it again. You should now be at (2, 5). Plot another point. Now, do it one more time. You should now be at (3, 8). Plot your last point. (If you wish to continue plotting additional points, feel free to do so.)

**5) Draw and label the line. **Use your ruler or straightedge to connect the dots, draw your arrows on both ends (to show it is a line), and label your line as "y = 3x -1"!

I hope this helps! Feel free to reply with any questions or comments.

Regards,

Vanessa

(The Math Lady)