An equation in the slope-intercept form is written as
Where m is the slope of the line and b is the y-intercept. You
can use this equation to write an equation if you know the slope
and the y-intercept.
Find the equation of the line
Choose two points that are on the line
Calculate the slope between the two points
We can find the b-value, the y-intercept, by looking at the
b = 1
We've got a value for m and a value for b. This gives us the
In many cases the value of b is not as easily read. In those
cases, or if you're uncertain whether the line actually crosses the
y-axis in this particular point you can calculate b by solving the
equation for b and then substituting x and y with one of your two
We can use the example above to illustrate this. We've got the
two points (-3, 3) and (3, -1). From these two points we calculated
This gives us the equation
From this we can solve the equation for b
And if we put in the values from our first point (-3, 3) we
If we put in this value for b in the equation we get
which is the same equation as we got when we read the
y-intercept from the graph.
To summarize how to write a linear equation using the
slope-interception form you
1. Identify the slope, m.
This can be done by calculating the slope between two known points
of the line using the slope formula.
2. Find the y-intercept. This
can be done by substituting the slope and the coordinates of a
point (x, y) on the line in the slope-intercept formula and then
solve for b.
Once you've got both m and b you can just put them in the
equation at their respective position.
Videolesson: Find the equation to the graph