Chapter 9 Quadratic Relations and Conic Sections - 9.4 Graph and Write Equations of Ellipses - 9.4 Exercises - Skill Practice - Page 637: 17

$$\frac{x^2}{25}+\frac{y^2}{9}=1$$

We know the following equation for an ellipse centered at the origin: $$\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$$ Where $(a,0)$ is the vertex and $(b,0)$ is the co-vertex. Thus, we find: $$\frac{x^2}{(5)^2}+\frac{y^2}{(-3)^2}=1$$ $$\frac{x^2}{25}+\frac{y^2}{9}=1$$