y^2/9 - x^2/16=1 has focii at ?

Question

y^2/9 - x^2/16=1 has focii at ?

 

a. (0.+-5)
b. (+-5,0)
c. (+-4,0)
d. (0,+-4)

Answer 1

A: (0,±5)

Answer 2

Hi Makenzie, we can find the foci by the following:

 

c² - a² = b²

 

Where a² = 9 and b² = 16

 

c² - 9 = 16

 

Add 9 to both sides:

 

c² = 25

 

Take the square root:

 

c = ±5

 

The center of the hyperbola is at: (h, k) or (0, 0)

 

Therefore, the foci are: (0, -5) and (0, +5)

 

The correct answer is a.

 

Questions?