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What is the equation of the line through (3, -1) and (4, 7).

1 Answer

4 votes

Answer:

y=8x-25

Explanation:

First, you want to find the slope.

Formula: y2-y1 / x2-x1

So, in this case it would be: 7-(-1) / 4-3

Which is the same thing as 7+1 / 4-3 = 8/1 or just 8

Now, when finding the equation of the line, always use the slope-intercept equation: mx + b = y.

If we plug in the slope, we get 8x + b = y. However, we want to find b, since we could use either (3, -1) or (4, 7) for the x and y.

I'm going to use (4, 7), but it doesn't matter what you choose because you'll get the same answer.

8(4) + b = 7.

When you simplify you should get b = -25.

So now, you just have to plug everything in and you get your answer y = 8x - 25.

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