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ACT Math 2.3 Coordinate Geometry 233 Views


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Description:

ACT Math: Coordinate Geometry Drill 2, Problem 3. What is the equation of the graph in the video?

Language:
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Transcript

00:02

And here's an unshmoopy question you may find on an exam somewhere in life...

00:06

What is the equation of this graph?

00:08

And here are your potential answers...

00:14

Alright... remember our old friend y equals mx plus b? It's the standard form to describe a line.

00:19

And the Rosetta stone in it is m. That is, the slope.

00:23

Since we have 2 points on this line, we can get that sucker straight away.

00:28

So... remember that slope is rise over run, or y2 minus y1 over x2 minus x1.

00:33

That'll give us a slope of 3 over -1.5 or just ... -2.

00:40

Now that we know m is -2, we can plug it into our equation to get y equals -2x plus b.

00:46

Now to find b...

00:48

To do that, we can just plug in one of the points. So let's just use 0, 3.

00:52

0 is the x value and 3 is the y value.

00:55

Plug in the variables and we get:

00:57

3 equals -2 times 0 plus b.

01:02

Well, -2 times 0 is 0... so b equals 3.

01:06

And our answer is C.

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