the amount of substance,kg in container at time t^2-5t+8 t(0 5) at what rate is the amount chang after 4hrs?

Answer 1

if tis in hours and
A = t^2 - 5t + 8
A' = 2t - 5
A'(4) = 8 - 5 = 3 kg/hr

If
A = t^2 - 5t + 8t^(0.5)
A' = 2t - 5 + 4/t^(0.5)
A'(4) = 8 - 5 + 2 = 5 kg/hr