# Thread: Modelling with exponential fuction.

1. ## Modelling with exponential fuction.

The growth rate of a plant during the first week after germination is given by g(t)=ae^(t/2) mm/day, where the time t is measured in days, and a is a constant.

a) Determine the height of the plant h(t) as a function of the time t, assuming that it was zero at time t=0.
b)On the first day, the plant grew 1 mm. Determine the constant a.
c) How much did the plant grow on the fifth day (i.e. between t=4 and t=5)?

I don't know if I'm doing this right. I got h(t)=a(2e^t/2 - 2) for part a and a=1 for part b. Is that right?

2. I'm assuming the information from A, B and C all apply throughout so:
I got the same equation but without the parenthesis for A. For B I got
a = $3/(2*sqrt(e))$. hope that helps

3. Originally Posted by AsSeenOnTV
I'm assuming the information from A, B and C all apply throughout so:
I got the same equation but without the parenthesis for A. For B I got
a = $3/(2*sqrt(e))$. hope that helps
How did you get that for part B?
And why aren't there parentheses for part A? Isn't "a" a constant, so you can take it out of the integral?

Edit:
Okay, I know how to get part B and for part C, I got (2e^5/2 - 2e^2)/(2sqrt(e)-2). Could you verify that you get the same answers as me for part b and c, using the equation I got in part a? And again, why is my part A answer different from yours?
Thanks!