# Thread: Help with a problem involving distance and midpoint?

1. ## Help with a problem involving distance and midpoint?

Hello! I posted this question the other day but when my friends and I compared our answers, some of them said their answer is only 4 and not ±4 like what I arrived at. The question and my solution to the problem are attached as pictures.

Shouldn't it be ±4 because whether A is (1,-4) or (1,4), its distance to the midpoint of D and Y will still be 4?

If not, can you please tell me where I went wrong?

Thank you very much for your help!

2. ## Re: Help with a problem involving distance and midpoint?

Originally Posted by kaonashi
Hello! I posted this question the other day but when my friends and I compared our answers, some of them said their answer is only 4 and not ±4 like what I arrived at. The question and my solution to the problem are attached as pictures.
Shouldn't it be ±4 because whether A is (1,-4) or (1,4), its distance to the midpoint of D and Y will still be 4?
If not, can you please tell me where I went wrong?
You are correct. $k=\pm 4$.