Identify the y-intercept. Then find another point that lies on the grid.
y=3x+4
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, 4). This means that the value of b is 4.
y= mx+ 4
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 (- 1,1) as our other point. Traveling to the y-intercept from this point requires that we move 1 step horizontally in the positive direction and 3 steps vertically in the positive direction.
rise/run=3/1 ⇔ m= 3
Writing the Equation
Now that we have the slope m= 3 and the y-intercept b= 4, we can write our final equation.
y= mx+ b ⇔ y= 3x+ 4
