Is there a bug in this math program?

**Is there a bug or am I simply making a mistake in the following example?:**

Question:

Find a function http://gauss.vaniercollege.qc.ca/web...22b824af51.png of http://gauss.vaniercollege.qc.ca/web...dd0b8b8e91.png such that http://gauss.vaniercollege.qc.ca/web...b39caf0291.png ?

__My Answer:__

sqrt(1/5 * x^2 - 1)

I ask because the program does not say that it's wrong but it doesn't say that it's right either. In fact, it says "Can't generate enough valid points for comparison." So, IF I am right, I am going to email my teacher to inform him so if anyone could confirm, it would be greatly appreciated!

Thanks in advance!