How to Write a Function From a Graph


Hi, I'm Rachel, and today we're going to be going over how to write a function from a graph. So let's say we have a graph like so and the main thing we want to do is identify two points on the graph. So let's say we have this point and this point. Let's say that this point is negative 1, 2 and this point is 0, 4. Well we want to write it as Y equals MX plus B. That's our slope intercept form and that's the most useful form for graphing a line. So we know that the Y intercept right which is the B, B stands for Y intercept is 0, 4. It intercepts at 4. That's where it intercepts the Y axis. This is the Y axis and this is the X axis. So B is going to B. That's where it intercepts. So we know we have Y equals MX plus 4. Now how do we find M? Well that is the slope of the lines. If we have the graph in front of us we can actually just count it because M is the rise over the run. That's what slope is. So we're at negative 1 and we can go up two, right, and over one. So the slope is actually going to be 2. So Y equals 2X plus 4 and that is how we find the equation of the line from the graph. I'm Rachel and thank you for learning with me today.

Rachel Kaplove has worked as a professional private tutor since 2005. Specializing in Math and Science, she tutors students from the second grade level to advanced high school honors levels.