What's the point?

WHAT’S THE POINT? Finding a missing coordinate

My High School Math I

ଷ

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

=

ଷ

ଷ

ଶ

௫మ ିଶ

=

ଷ ଶ

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); ݉ =

ଷ ସ

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