# Hyperbola and Elipse Equations

• November 12th 2009, 08:38 AM
Mr.Berlin
Hyperbola and Elipse Equations
Need help with these...or more like I forget algebra.

$4y^2 - x^2 = 1$

$4y^2 + x^2 = 1$

Thanks.
• November 12th 2009, 09:48 AM
bigwave
$4y^2 - x^2 = 1$
this is a hyperbola with the foci on the y axis
the general equation is:

$\frac{y^2}{a^2} - \frac{x^2}{b^2} = 1$

where $b^2 = c^2 - a^2$
$c > a, c > b$

$4y^2+ x^2 = 1$
this is an ellipse

the general equation is:
$\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$
where $b^2 = a^2 - c^2$
$a > b, a > c$
• November 12th 2009, 01:40 PM
Mr.Berlin
Yeah, so I have to eliminate the coefficient. Thats' what I can't remember how to do.
• November 12th 2009, 01:51 PM
bigwave
basically
complete the square
• November 12th 2009, 02:23 PM
Mr.Berlin
Quote:

Originally Posted by bigwave
basically
complete the square

Actually I remembered, as obvious as it seems...

$4y^2$ = $\frac{y^2}{\frac{1}{4}}$ = $\frac{y^2}{\frac{1}{2}^2}$