I need this explained....

Hello,

My notes have** y=sqrt x^2-16**

Now it's -4 and 4 on the x axis, but just the top part of the y curve, as it starts with that. going out to each side.

So the fixing up the equation above is y^2=x^2-16

so y^2-x^2=-16 which turns into x^2-y^2=16.

Now x^2=16 is x=4, But for y it's y = -4, but how does that work? I need x -4,+4.

I don't understand how to come up with the -4 on x.

Does this make sense? it's hard to write out without a graph.

Graphing Calculator

If you go to this graphing online you will see what I am talking about keying in the above equation in bold

If someone can explain this would be great, thanks.

Joanne

just trying to understand it, because I am not getting it.