How do you write an equation for the hyperbola with center (0,0), vertex (-2,0) and focus (4,0)?

1 Answer
Oct 30, 2016

Please see the explanation.

Explanation:

The given, center, vertex, and focus share the same y coordinate, 0, ,therefore, the standard form for the equation of this type of hyperbola is the one corresponding to the Horizontal Transverse Axis type:

(x - h)^2/a^2 - (y - k)^2/b^2 = 1

where (h, k) is the center, a is distance from the center to the vertex, and b affects the distance, c, from the center to the focus as determined by the equation c^2 = a^2 + b^2.

Substitute the center (0, 0) into the standard form:

(x - 0)^2/a^2 - (y - 0)^2/b^2 = 1

We know that a = 2, because one of the vertices a distance of 2 from the center. Substitute 2 for a into the equation:

(x - 0)^2/2^2 - (y - 0)^2/b^2 = 1

Observing that the focus is a distance of 4 from the center we set c^2 = 16 in the equation c^2 = a^2 + b^2:

16 = a^2 + b^2

Substitute 4 for a^2

16 = 4 + b^2

Solve for b:

b= sqrt(12)

Substitute sqrt(12) for b into the equation:

(x - 0)^2/2^2 - (y - 0)^2/(sqrt(12))^2 = 1