Calculus
H′(90)=−15H^{\prime}\left(90\right)=-\frac15
At t=90 dayst=90\text{ days}, the plant is shrinking at a rate of 15 cm/day\frac15\text{ cm/day}.
H′(90)=15H^{\prime}\left(90\right)=\frac15
At t=90 dayst=90\text{ days}, the plant is growing at a rate of 15 cm/day\frac15\text{ cm/day}.
At t=90 dayst=90\text{ days}, the plant is growing at a rate of 5 cm/day5\text{ cm/day}.
At t=90 dayst=90\text{ days}, the plant is shrinking at a rate of 5 cm/day5\text{ cm/day}.