ShmoopTube

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And here's your shmoop du jour.

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The points (2, 5) and (3, 9) lie on the same line. The equation of this line is… what?

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And here are the potential answers…

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So… what is this question asking?

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It’s asking for another way to make y equals mx plus b.

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To plus b or not to plus b… is that the question?

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Anyway… slope is rise over run… so when we have 2 points, we can find the rise by

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subtracting the two y points and putting them in the numerator…

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…and we can find the run by putting the two subtracted x points in the denominator.

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In this case, we get the m, or slope, by subtracting 5 from 9 to get 4; that’s our “rise”…

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The run is the x difference, so we subtract 2 from 3 to get 1.

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Our slope is 4 over 1, or just 4. Positive 4.

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Now we have to find b – we have everything else so we can just plug in some numbers:

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y = mx + b, so by using point 2, 5 we get:

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5 = 4 times 2 + b…

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…or 5 = 8 + b…

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…or b = 5 – 8…

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…or b = -3.

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So it’s… y = 4x -3…. Answer C.

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As in, “Caught it.”

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