Identify the y-intercept. Then find another point that lies on the grid.
y=- 2x+8
Practice makes perfect
Equations written in slope-intercept form follow a specific format.
y= mx+ b
In this form, m is the slope and b is the y-intercept. We need to identify these values using the graph.
y-intercept
The y-intercept is the y-value where the line crosses the y-axis.
We can see that the function intercepts the y-axis at (0, 8). This means that the value of b is 8.
y= mx+ 8
Slope
To find the slope, we will trace along the line on the given graph until we find a lattice point, which is a point that lies perfectly on the grid lines. Doing so, we can identify the slope m using the rise and run of the graph.
Here we have identified the x-intercept at (4,0) as our other point. Traveling to the y-intercept from this point requires that we move 4 steps horizontally in the negative direction and 8 steps vertically in the positive direction.
rise/run=8/- 4 ⇔ m= 8/- 4
Writing the Equation
Now that we have the slope m= 8- 4 and the y-intercept b= 8, we can write our final equation.
