Chapter 9 - Analytic Geometry - Section 9.3 The Ellipse - 9.3 Assess Your Understanding - Page 677: 27

$\frac{x^2}{25}+\frac{y^2}{16}=1$ See graph.

1. Based on the given conditions, we have $a=5, c=3$, center $(0,0)$ with a horizontal major axis, thus $b=\sqrt {a^2-c^2}=\sqrt {25-9}=4$, and $\frac{x^2}{25}+\frac{y^2}{16}=1$ 2. See graph.