Slope Intercept Form

Standard

F.IF.7.a Graph functions and show intercepts, maxima, and minima.

Goals for this section:

Students will learn what a slope-intercept form looks like. They will be able to identify the slope and the y-interccept and how to create a graph using only those pieces of information.

Slope (m)

Slope describes how much a line "rises" and "runs".

    • "Rise" corresponds with vertical movement (up and down directions). It is the numerator/top part of the fraction.
    • "Run" corresponds with horizontal movement (left and right directions). It is the denominator/bottom part of the fraction.

Recall this from the previous lesson:

Tips for finding the slope graphically:

    • Start with the left-most point!
    • Determine your rise. If it goes up, it's a positive number. If it goes down, it's a negative number.
    • Determine your run. If you started with the left-most point, your run will always be positive since it will be going to the right, which is the positive direction.

What if you're not given points on the graph? Like there's no dots?

    • Make your own dots! So long as your dots are on the line and you can find (x,y) coordinates out of them.

y-intercept (b)

The y-intercept is where the line crosses the y-axis.

      • The y-axis is the axis that points up and down.
      • There can be cases where a "line" does not cross the y-axis. Refer to the next tutorial about Horizontal and Vertical lines.

So for this graph, b = -3. Your y-intercept is at -3.

Examples

1. Graph y = 2x - 1.

Step 1: Plot the y-intercept.

Step 2: Apply slope.

Step 3: Connect the two lines!

2. Create a slope-intercept equation (y=mx+b) of the graph. This means to identify m and b.

Step 1: Is the y-intercept easily identifiable?

Step 2: Find the slope. Pick two identifiable points on the graph and use them to find the slope.

Step 3: Plug in m and b into the slope-intercept equation.

3. Create a slope-intercept equation given (-2,-8) and (2,2).

Step 1:

External Resources


This video gives an overall review of Slope-intercept form to get a more clear understanding of the material.

Keywords: slope, slope intercept form, y-intercept, y = mx + b, rise run