Nathan B. answered • 09/08/16

Elementary and Algebraic skilled

We know how to find the midpoint coordinates by the following:

(a + b) / 2 = c, where a and b are the endpoints and c is the midpoint.

Well, in this case, instead of a and b and finding c, we have a and c, and need to find b. First the x-coordinate:

(3 + b) / 2 = 6

multiply both sides by 2:

3 + b = 12

Subtract both sides by 3:

b = 9

Now the y- coordinate. Follow the same rules as before, start by multiplying by 2:

(3 + b) / 2 = 9

3 + b = 18

Subtract 3:

b = 15

So our missing endpoint is (9, 15).