• May 5th 2009, 12:02 PM
tiga killa
write the equation of the hyperbola with vertices (+-3,0) and asymptotes y= +-4x

write the equation of the sphere with center (1,4,-3) and tangent to the xz plane.

help me out
• May 5th 2009, 12:17 PM
Opalg
Quote:

Originally Posted by tiga killa
write the equation of the hyperbola with vertices (+-3,0) and asymptotes y= +-4x

The equations of the asymptotes are $\displaystyle y+4x=0$ and $\displaystyle y-4x=0$. Multiply these together to get $\displaystyle y^2-16x^2 = 0$. The equation of the hyperbola will then be $\displaystyle y^2-16x^2 = k$, where k is chosen so that the points (±3,0) lie on the curve (namely k=–144). You can then rearrange the equation in the form $\displaystyle \frac{x^2}{3^2} - \frac{y^2}{12^2} = 1$ if you want it to look like a standard hyperbola equation.

(That method will always work. Start by multiplying the equations of the asymptotes together, then change the constant term so that the curve goes through the specified point.)
• May 5th 2009, 12:36 PM
tiga killa
thanks,,

equation of a sphere??