Question 130147
The height h of the ball, in feet, x seconds after the ball is thrown is given by the equation. 
h(t)= -2.7x^2+30x+6.5 
After how many seconds is the ball 12 feet above the moon's surface?
-----------
Let the height be 12 and solve for "x".
-2.7x^2 + 30x + 6.5 = 12
-2.7x^2 + 30x - 4.5 = 0
x = [-30 +- sqrt(900 -4*-2.7*-4.5)]/-5.4

x = [-30 +- sqrt(851.4)]/-5.4

x = [-30 +- 29.17876]/-5.4

x = 10.96 seconds and x = 0.1521 seconds
==========================
Cheers,
Stan H.