Posted by **Lucy** on Sunday, October 12, 2008 at 2:00pm.

Find the equation of the hyperbola whose vertices are at (-1,-5) and (-1,1) with a focus at (-1,-7).

So far I have the center at (-1,-2) and part of the equation is (y+2)^2 - (x+1)^2 but do not know how to figure a^2, b^2, or c^2.

Help please....

- Pre-Calculus -
**bobpursley**, Sunday, October 12, 2008 at 2:27pm
Hmmm. I don't know what you mean by c.

(y+2)^{2}/a^{2} -(x+1)^{2}/b^{2} = 1

You have two points for x,y, that should give you two equation to solve for a, b.

- Pre-Calculus -
**Damon**, Sunday, October 12, 2008 at 2:31pm
center to vertex = a = 3

center to focus = sqrt(a^2+b^2) = 5

so 9+b^2 = 25

b = 4

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