Chapter 2.2, Problem 39E

Projectiles Two projectiles are shot into the air from the same location. The paths of the projectiles are parabolas and are given by

$y=-0.0013x^2+x+10$ and

$y=\frac{-x^2}{81}+\frac{4}{3}x+10$ where x is the horizontal distance and y is the vertical distance, both is feet. Determine which projectile goes higher by locating the vertex of each parabola.