Calculus
posted by Joe Schmo .
The rate of change R, in kilometers per hour, of the altitude of a hot air balloon is given by R(t)=t^34t^2+6 for time on the interval [0,4], where t is measured in hours. Assume the balloon is on ground level.
What is the maximum altitude of the balloon during the interval [0,4]?

Find dR/dt, set equal to zero, find time. PUt that in the original equation for altitude.
R'=3t^28t=0
t(3t8)=0
t=0, t= 8/3 sec
Rmax=R(8/3)= you do it. 
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