# Math Help - conics

1. ## 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

2. 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.

3. 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

4. The quadradic in form of,
$
ax^2+2hxy+by^2+2gx+2fy+c=0$

can de determined by looking a the relationship between,
$h^2$ and $ab$.

$h^2=ab$---->parabola
$h^2>ab$---->hyperbola
$h^2---->ellipse
In your case we have #2 which is a hyperbola.

[Note: Some cases where not considered such as the coditions for a general quadradic to represent a line or to represent a point]