# conics

• July 8th 2006, 07:01 PM
Lane
2 math questions:p
Which equation describes a circle?
A: -2y2+y+2x2-5x-3=0
B: -3x2+x-6y2+y=4
C: -3y2+x+y=3

Identify the conic section with the given equation 5x2-6y2-9x+2y+3=0

p.s. the twos are supposed to be raised to that power
• July 8th 2006, 10:33 PM
rgep
None of those is a circle. In a general quadratic form, if the coefficients of x^2 and y^2 are equal, it's a circle; unequal but the same sign, an ellipse; one zero and one non-zero, a parabola; of different sign, a hyperbola (rectagular if the coefficients are equal in absolute value). So you have a rectangular hyperbola, an ellipse and a parabola respectively.
• July 8th 2006, 10:46 PM
earboth
Quote:

Originally Posted by Lane
...
Identify the conic section with the given equation 5x2-6y2-9x+2y+3=0
...

Hello, Lane,

as rgep explained this equation describes a hyperbola.

Greetings

EB
• July 9th 2006, 05:27 AM
ThePerfectHacker
$
$h^2$ and $ab$.
$h^2=ab$---->parabola
$h^2>ab$---->hyperbola
$h^2---->ellipse