Posted by **Jed** on Friday, May 6, 2011 at 1:07am.

Hyperbolas:

Could someone please tell me how to determine if the following indicate the foci are on the x-axis or the y-axis?

x^2/4 -y^2/16 = 1

x^2/49 - y^2/9 = 1

x^2/36 - y^2/16 = 1

please explain how to set the equations up

thank you

- Algebra II -
**Damon**, Friday, May 6, 2011 at 4:01am
These are all hyperbolas.

Look at wwhat happens when y = 0 (on the x axis) and when x = 0 (on the y axis)

In all cases, when y = 0, there are two real solutions for x. In the first one for example when y = 0, x = 2 or x = -2

However when x = 0, there is no real solution for y. In other words the hyperbolas never reach the y axis and open left and right. All foci are therefore located on the x axis.

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