## Precalculus (6th Edition) Blitzer

Step 1. Given $\frac{(x-4)^2}{4}+\frac{(y)^2}{25}=1$, we have $a^2=25, b^2=4$ and $c=\sqrt {a^2-b^2}=\sqrt {21}$. The ellipse is centered at $(4,0)$ with a vertical major axis. Step 2. We can graph the equation as shown in the figure with foci at $(4,\pm\sqrt {21})$.