ShmoopTube

00:03

And here's your shmoop du jour.

00:05

Which of the following could be the graph of the equation y equals negative two-thirds x-cubed?

00:11

Here are the potential answers...

00:13

Before we spoil the ending, hit pause and try to solve it yourself.

00:20

What is this question really asking?

00:22

Well, it's really about visual patterning.

00:24

That is, the first thing it's asking is "which way does the line slope?"

00:29

In this case, the equation is clearly written in the y equals m x plus b standard form for a line...

00:35

Only, b is ... zero... and x is... x cubed.

00:38

The m is right here; it's negative 2 thirds...

00:42

...so.... a NEGATIVE slope means the line slopes downward like this -- and remember

00:47

a positive slope would run like this...

00:49

...and a slope of zero is just a dead man's pulse. Yeah. Sad.

00:54

A negative slope heads from Seattle to Miami,

01:02

so we can cross out potential answer A anyway

01:05

because it goes more from... ...San Diego to New York.

01:09

The next element is that this equation is in the form y equals x cubed.

01:15

That means it'll be this S-shape... so we can kick out equation C because it's a parabola's formula.

01:21

We need an S-shape that trends down and the only one that fits the map... is B.

01:30

We'll be sure to have this graph on display at the funeral. Bubbles would have loved this.

Full Transcript