A creature on the moon throws a rock off a cliff. The height of the rock above the surface of the moon, in meters, t seconds after it is thrown is given by h(t)=-t^2 +8t+10. When does the rock hit the surface of the moon?
+128470 When it hits the surface, the height = 0...so
-t^2 + 8t + 10 = 0
Use the quad formula
-8 ± sqrt [ 8^2 - 4 * -1 * 10 ] -8 ± sqrt [ 104] -8 ± 2sqrt (26)
_______________________ = _____________ = _____________ =
2 (-1) -2 -2
4 -sqrt (26) sec (reject) or
4 + sqrt (26)sec ≈ 9.1 sec
