math
posted by bill .
A projectile is fired directly upward with a muzzle velocity of 860 feet per second from a height of 7 feet above the ground.
a. Determine a function for the height of the projectile t seconds after it’s released.
b. How long does it take the projectile to reach of height of 100 feet on its way up?
c. How long is the projectile in the air?

math 
Reiny
height(t) = 16t^2 + 860t + 7
b) solve 100 = 16t^2 + 860t + 7 and use the smaller of the two t values you find
c) set height(t) = 0 and solve
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