The equation y = -6t^2 + 51t describes the height (in feet) of a projectile launched from the surface of Mars at 51 feet per second. In how many seconds will the projectile first reach 108 feet in height?
y = -6t2 + 51t
y = 108
Combining: -6t2 + 51t = 108
-6t2 + 51t - 108 = 0
Multiplying by -1: 6t2 - 51t + 108 = 0
Dividing by 3: 2t2 - 17t + 36 = 0
Factoring: (2t - 9)(t - 4) = 0
Answer: Either t = 4.5 or t = 4
