## Precalculus (6th Edition) Blitzer

Step 1. Given the equation $\frac{x^2}{25}+\frac{y^2}{4}=1$ for an ellipse, we have $a=5,b=4,c=\sqrt {a^2-b^2}=3$ with a horizontal major axis, center at $(0,0)$, and foci at $(\pm3,0)$ Step 2. We can graph the equation as shown in the figure.