WHAT’S THE POINT? Finding a missing coordinate
My High School Math I
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Given two points, (2,3) and (ݔ, 6)and slope is . Find ݔ. ଶ
Use the formula:
௬మ ି௬భ ௫మ ି௫భ
Plug in for what you know and
solve for what you don’t know! ିଷ ௫మ ିଶ
=
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ଷ
ଶ
௫మ ିଶ
=
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Cross multiply: 3(ݔଶ − 2) = 3(2) Distribute on the left and multiply on the right! Simplify!
Divide each side by 3!
3ݔଶ − 6 = 6 +6 + 6 3ݔଶ = 12 3ݔଶ 12 = 3 3 ݔଶ = 4
Add 6 to each side!
Simplify!
Now let’s see how to do this same problem, But we will look at it on a graph! ଷ
The slope is . ଶ
So from the point on the graph we can go two ways. We can go up 3 and right 2. Or we can go down 3 and left 2.
We need to keep in mind the other point we were given. It has a y-coordinate of 6. We need the point in blue, because the y-coordinate is 6! We can see that the x-coordinate is 4!!
Now it is your turn! Find the missing coordinate! Try to find it using the slope formula. 1. (−1, )ݕand (3,5); ݉ =
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2. (ݔ, −3) and (2, −1); ݉ = −1 3. (−6, −2) and (4, = ݉ ;)ݕ 4. (5, −2) and (ݔ, 4) ; ݉ =
ଶ ହ
ିଷ ସ
Remember when the slope is a whole number or an integer, you can always write it as a fraction. The bottom number (denominator) will be 1! Written by Genny Phillips 3/19/2015