The height h, in feet, of a projectile t seconds after launch is modeled by the equation h = 32t- 16t^2. how long after does the projectile return to the ground?

Hello : 
the projectile return to the ground when : 32t- 16t² =0
16t (2-8t) = 0
16t = 0   or 2-8t = 0
t = 0   ( refused) or t = 1/4
after 1/4 s the projectile return to the ground

Dang i wish i could , good luck (i’m bad at math)