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For those of you who watch or play football, then you are familiar with the term 'interception.' For those of you who aren't, well, stop and think for just a second what interception just might mean… Why all this talk about football? Isn't this a website about math? Yeah, sure but let's take a look at football for a second and then make the connection to math, shall we? |
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In a linear equation, y = mx + b,
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In football, a quarterback (offensive player) for team A throws a pass. Unfortunately, a defensive player from team B intercepts the ball before someone from team A can catch it. |
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Team B is thrilled! They have thwarted the other team! Bummer for Team A… So, how does all of this relate to math and linear equations? |
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Pretend that the quarterback is throwing the ball and the path it is taking is the line. Here is a picture to help you 'get' it. We always read from left-to-right so the quarterback is on the left. He throws the ball to the right so the ball is going UP. Let's see what happens. |
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Team B (the y-axis) intercepts the pass. In this picture, the point of interception is circled. This means that the point where the line crosses the y-axis is the point of interception or the y-intercept. The point the line crossed is at (0, 2). In the linear equation formula, y = mx + b, think of the b as ball. In a coordinate pair your numbers are set up (x, y). If we are looking for the 'y' for our ball for the y-intercept, which one would it be from our point? Did you say 2? Hooray! Just substitute THAT number in the equation!
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Cool! Now that you understand the vocabulary from a football point-of-view and you know the definition of what a y-intercept is, let's see how you can find the y-intercept from looking at a graph. |
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Step 1: Look at the line. Find where it crosses the y-axis. |
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Step 2: Draw a CIRCLE around the point where the line crosses the y-axis. |
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Step 3: Write down the basic linear equation form y = mx + b. Substitute the number you circled for the b. |
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Step 4: Go find the slope to finish your equation! y = mx + b. |
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©2011–2017 Sherry Skipper Spurgeon. All rights reserved. |
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