Question

Point Q lies on the circle and has an x-coordinate of 4.


Which value could be the y-coordinate for point Q?

2
4
2
8

Answer 1

I don't have the circle's equation or diagram — could you post the circle's equation or the picture? With that I can plug x = 4 into the circle equation and solve for y.

How to do it (so you can check while you post the missing info):
- If the circle has equation (x − h)^2 + (y − k)^2 = r^2, substitute x = 4 to get (4 − h)^2 + (y − k)^2 = r^2.
- Solve (y − k)^2 = r^2 − (4 − h)^2, so y = k ± sqrt(r^2 − (4 − h)^2).
- If r^2 − (4 − h)^2 is negative, no point on the circle has x = 4. If it is zero you get one y, otherwise two y values.

Also, your answer choices list 2 twice — did you mean to have a different fourth choice?