Chapter 9 Quadratic Relations and Conic Sections - 9.4 Graph and Write Equations of Ellipses - 9.4 Exercises - Problem Solving - Page 639: 52c

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The focal radius from A to the rightmost vertex is the same as the focal radius from A to that vertex. The focal radius from B to that vertex is the same as the focal radius from B to that vertex. The total distance flown is 600 miles since the sum of the focus radii is constant. The distance from the center to a vertex on the major axis is $a$: $2a=600 \rightarrow a=300$ The coordinates of the vertex are: $(-300,a)$ and $(300,0)$