2. The graph of the equation
\frac{x {}^{2} }{a {}^{2} } + \frac{y {}^{2} }{a {}^{2} } = 1
a
2

x
2

​
+
a
2

y
2

​
=1
with
a > b > 0a>b>0
is an ellipse with vertices (_,_) and (_,_) and foci (±c, 0), where c=___. So the graph of
\frac{x {}^{2} }{5 {}^{2} } + \frac{y {}^{2} }{4 {}^{2} } = 1
5
2

x
2

​
+
4
2

y
2

​
=1
is an ellipse with vertices (_,_) and (_,_) and foci (_,_) and (_,_).​