find the foci of the ellipse x^2/7+y^2/16=1?

Answer 1

The ellipse is vertical. y²/a² + x²/b² = 1.

a = 4; b = √7
c = 3 since a² = b² + c²

center at the origin.

foci: (0,±3)

d:

Answer 2

x² / a² + y² / b² = 1 is equation of ellipse centre(0,0)
In this case a² = 7 and b² = 16
Major axis lies along y axis and e is given by
a² = b²(1 - e²)
7 = 16(1 - e²)
7 / 16 = 1 - e²
e² = 9 / 16
e = 3 / 4
Focii are (0, ± be)
Focii are (0, ± 4e)
Focii are (0, ± 3)