hint; max ht is when velocity=0.A small marshmallow is launched straight up in the air with a slingshot. Its heighthin meters, relative to te ground, is given by the functionh(t)= 5 + 20 - 5t^2, wheretis measured in seconds. About when does the marshmallow reach its maximum height?

v=dh/dt.

and as said previous you are missing a t.

*h*(

*t)*= 5 + 20t - 5

*t*^2