Things You'll Need:
- pen/pencil
- paper
- calculator
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Step 1
Start by writing y=mx+b. Here, m is the slope of the line, b is the y intercept of the line, and x and y are the x- and y-coordinates, respectively, of any point on the line.
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Step 2
Plug the value of m into the equation. In some problems, you will not be given m directly. Instead, you will be given two points and have to find the slope from this information. Take a look at my eHow article "How to Calculate the Slope of a Line, Given Two Points On That Line" if you forget how to find slope.
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Step 3
Now you can find b. Plug in the x-coordinate and the y-coordinate of the point you are given.
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Step 4
Solve for b.
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Step 5
Now that you have all of the information, write your answer in y=mx+b form.
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Step 6
Let us do an example. Write the equation of the line that goes through (4,2) and (8,10). Here, we would start by writing y=mx+b. The slope, m, is (10-2)/(8-4) which is 8/4 or 2. Now we have y=2x+b and must find b. We can choose either (x,y) point to insert and then solve for b. We will use (4,2), so we have 2=2(4)+b. Solving for b yields 2=8+b, so b= -6. The answer is then y=2x+(-6) which is y=2x-6.
