- The following two equations describe the height of a missile above (or below) the surface of the ocean, when it is launched from a submarine:
- $ y = -t^2 + 12t - 20 $
- $ y = -5t^2 + 30t - 20$
- After how many seconds will each missile break through the surface of the water?
- After how many seconds will each missile crash back into the water?
- For how many seconds is each missile above the surface?
- Hint: $t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$