ShmoopTube

00:03

Here’s your shmoop du jour…

00:05

What is the equation of the graph shown below?

00:08

And here are the potential answers…

00:13

So… what is this question asking?

00:15

Can we make an equation out of thin air?

00:17

Just watch as we do our best David Blaine impression…

00:20

Y equals mx plus b is the standard point slope form of an equation

00:24

and there are a few ways to get the answer.

00:27

For starters, we can figure out the slope of the line just by looking at the graph and

00:31

finding the y intercept, and… we’re pretty much there.

00:34

So if we look at the line, it heads downward into the great abyss,

00:38

so we know that the slope, or m, is gonna be negative.

00:42

How negative? Well, slope is rise over run.

00:45

In this case, the rise – or anti-rise – goes

00:49

down two for every one that the line moves horizontally…

00:54

…which gives us a slope of negative 2. Note that the line intersects the y axis at

00:59

negative 1… so we know that b is negative y.

01:02

Now we have our equation – y equals negative 2x minus 1.

01:06

And our answer is D.

01:07

As in, “David Blaine.”

Full Transcript