A dolphin jumps straight up from the water. The quadratic function y = −16t^2 + 20t models the motion of the dolphin, where t is the time in seconds and y is the height of the dolphin, in feet. Use the discriminant to explain why the dolphin does not reach a height of 7 feet.
+130511 I'm not sure if this is what you want, or not....
Since "c" = 0 in the quadratic formula....the discriminant is just b^2 = 20^2
The roots of this function will be [ -20 ± 20] / [2*-16) t = 0 and t = -40/-32 = 5/4 [seconds]
Due to the parabola's symmetry, the max height will be reached half-way between these two t values = at 5/8 seconds......
So....the max height is
-16(5/8)^2 + 20(5/8) = 25/4 ft = 6.25 ft
[Maybe some other mathematician sees something else here that I don't ???]
