Originally Posted by

**jonnygill** Hi!

i am trying to determine if this equation is symmetrical to the x-axis and/or the y-axis. or both. the equation is...

$\displaystyle y=\sqrt{2-a^2}$

which i changed to...

$\displaystyle y^2=2-a^2$

the book states that this equation is ONLY symmetrical to the y-axis. i agree it is symmetrical to the y-axis, but it also seems to me to be symmetrical to the x-axis.

since...

$\displaystyle (-y)^2=2-a^2 \Rightarrow y^2=2-a^2$

Because a square root has both a positive and negative value, doesn't this make sense?

what am i missing/misunderstanding?

p.s. is this algebra or pre-calc? i wasn't entirely sure