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CAHSEE Math 3.4 Algebra I 239 Views


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Description:

Algebra I Drill 3 Problem 4. What is the equation of the line shown in the graph?

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English Language

Transcript

00:03

And here's your shmoop du jour...

00:05

What is the equation of the line shown in the graph below?

00:09

And here are the potential answers…

00:14

So… what is this question asking?

00:16

Can we, like Superman, just look at a graph and come up with the equation?

00:20

Sure we can. Unless slope-intercept form is our Kryptonite…

00:24

Well, we know the y equals mx plus b format, and that approach should fit easily here,

00:30

since we need 2 things to make a linear equation – the slope and a point at which it intersects.

00:35

Just by looking at the line we know the slope is positive,

00:38

because it moves in an upward direction from left to right.

00:42

Since we know slope is rise over run, we can just figure this thing out.

00:46

Note that if we go forward 3 hops from the x intercept to the origin and then look straight up…

00:52

we see 4 hops above us.

00:54

So we rise 4 units for every 3 we run and that gives us a slope of 4 thirds.

01:01

Now we plug in the y intercept, which is here at 0, 4 –

01:05

i.e. where the line crosses the y axis.

01:08

That positive 4 is our “b.”

01:10

And if we glance at the answers, we can see ‘em right here… it’s gotta be A because

01:14

C and D have the wrong slope and intercept, and B has the wrong slope sign.

01:19

A it is. As in, "Action hero."

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