Question

An evergreen nursery usually sells a certain shrub after 6 years of growth and shaping. The growth rate during those 6 years is approximated by dh/dt = 1.5t+5 where t is the time in years and h is the height in centimeters.

The seedlings are 12 cm tall when planted.
a. Find the equation h(t) after t years.
b. How tall are the shrubs when they are sold?

Answer 1

a. To find the equation h(t) after t years, we need to integrate the given growth rate dh/dt = 1.5t + 5 with respect to t. This gives us:

h(t) = ∫(1.5t + 5) dt = (1.5/2)t^2 + 5t + C = 0.75t^2 + 5t + C

where C is the constant of integration. We can find the value of C using the initial condition that the seedlings are 12 cm tall when planted (i.e., when t = 0). Substituting these values into the equation above, we get:

h(0) = 0.75(0)^2 + 5(0) + C = 12 C = 12

So, the equation for the height of the shrub after t years is:

h(t) = 0.75t^2 + 5t + 12

b. To find out how tall the shrubs are when they are sold, we need to evaluate h(t) at t = 6, since the shrubs are sold after 6 years of growth and shaping:

h(6) = 0.75(6)^2 + 5(6) + 12 = 27 + 30 + 12 = 69

So, the shrubs are 69 cm tall when they are sold.

Explanation: