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This equation is a hyperbola in the form
(this hyperbola opens left/right).
for any hyperbola in the form
are (h+c,k) and (h-c,k) where
In this case,
which means that
Now plug in the given h, k, and c values into (h+c,k) and (h-c,k) to get:
and simplify to get
So the foci are
Note: the foci approximate to (4.4722, 0) and (-4.4722, 0)