Answer
Foci:
$(0, -4\sqrt{2})$ and $(0,4\sqrt{2}).$
Work Step by Step
Major axis parallel to the $y$-axis, vertical.
$a^{2}=81,$
$a=9$
$b^{2}=49,$
$b=7$
Vertices: $(h, k-a),\quad (h, k+a) $
$(0, -9),\quad (0, 9) $
Foci are $c$ units above and $c$ units below the center,
$c^{2}=a^{2}-b^{2}=81-49=32$
$c=\sqrt{32}=4\sqrt{2}$
Foci:
$(0, -4\sqrt{2})$ and $(0,4\sqrt{2}).$
