y = -3x + 4
The equation of a line is written in slope-intercept form.
[tex]y = mx + b[/tex]
- m = slope
- b = y-intercept
Slope is the rate of change, calculated by the rise of the graph divided by the run.
As you can see, the graph rises by a negative amount (top left to bottom right). Between two given points, the graph rises (or falls) by -3 units.
The graph also runs 1 unit between two points.
The slope is -3/1, or -3. We plug this value for "m".
The y-intercept is the point in which the graph intersects the y-axis. We can see the intersection at point (0,4). We simply take the y-value and plug it in for "b".
Given the slope of -3 and the y-intercept of 4, the equation of the line is [tex]y = -3x + 4[/tex].