Solve this Calculus Problem

Josh

Lifer
Mar 20, 2000
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0
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Let P(t) represent the number of wolves in a population at time t years, when t is greater than or equal to 0. The population P(t) is increasing at a rate directly proportional to 800 - P(t), where the constant of proportionality is k.

(a) If P(0) = 500, find P(t) in terms of t and k
(b) If P(2) = 700, find k
(c) Find lim P(t).
t --> infinity
 

Tiamat

Lifer
Nov 25, 2003
14,068
5
71
why do you need this solved? homework?
this is a very simple elementary differential equations question. Have you tried it? What are your answers? If you still have trouble, i can look at it.
 

Josh

Lifer
Mar 20, 2000
10,917
0
0
Originally posted by: Tiamat
why do you need this solved? homework?
this is a very simple elementary differential equations question. Have you tried it? What are your answers? If you still have trouble, i can look at it.

I thought is was Exponential Growth & Decay. We got a couple of answers but those don't have anything to do w/ the 800-P(t). Thanks in advance for your help.
 

nycxandy

Diamond Member
Apr 11, 2001
3,731
0
76
Originally posted by: Josh
Originally posted by: Tiamat
why do you need this solved? homework?
this is a very simple elementary differential equations question. Have you tried it? What are your answers? If you still have trouble, i can look at it.

I thought is was Exponential Growth & Decay. We got a couple of answers but those don't have anything to do w/ the 800-P(t). Thanks in advance for your help.

LOL? You're not asking for help. You're asking us to solve the answers for you. :thumbsdown:
 

Josh

Lifer
Mar 20, 2000
10,917
0
0
Originally posted by: nycxandy
Originally posted by: Josh
Originally posted by: Tiamat
why do you need this solved? homework?
this is a very simple elementary differential equations question. Have you tried it? What are your answers? If you still have trouble, i can look at it.

I thought is was Exponential Growth & Decay. We got a couple of answers but those don't have anything to do w/ the 800-P(t). Thanks in advance for your help.

LOL? You're not asking for help. You're asking us to solve the answers for you. :thumbsdown:

I'm looking for an explanation because I am stuck.
 

Josh

Lifer
Mar 20, 2000
10,917
0
0
Originally posted by: Random Variable
Originally posted by: JohnCU
Originally posted by: Random Variable
I get p(t)=800-300*exp[(-ln3/2)*t]

e^ln(x) = x
sorry

p(t)= 800-300*3^(-t/2)

which doesn't really simplify matters

howd you arrive at this conclusion?

(this question is for my cousin - not for me & i am not familiar with calculus)
 
Aug 10, 2001
10,420
2
0
Originally posted by: Josh
Originally posted by: Random Variable
Originally posted by: JohnCU
Originally posted by: Random Variable
I get p(t)=800-300*exp[(-ln3/2)*t]

e^ln(x) = x
sorry

p(t)= 800-300*3^(-t/2)

which doesn't really simplify matters

howd you arrive at this conclusion?

(this question is for my cousin - not for me & i am not familiar with calculus)

dp/dt=k(800-p)
?dp/(800-p)=?kt
-ln(800-p)=kt + c
800-p=e^(-kt+c)
p=800-e^(-kt+c)=800-c*e^(-kt)

p(0)=500=800-c
c=300

p(2)=700=800-300*e^(-2k)
1/3=e^(-2k)
ln3=2k
k=ln3/2

p(t)=800-300*e^[-(ln3/2)t]=800-300*3^(-t/2)



 

TuxDave

Lifer
Oct 8, 2002
10,571
3
71
Originally posted by: Random Variable
Originally posted by: Josh
Originally posted by: Random Variable
Originally posted by: JohnCU
Originally posted by: Random Variable
I get p(t)=800-300*exp[(-ln3/2)*t]

e^ln(x) = x
sorry

p(t)= 800-300*3^(-t/2)

which doesn't really simplify matters

howd you arrive at this conclusion?

(this question is for my cousin - not for me & i am not familiar with calculus)

dp/dt=k(800-p)
?dp/(800-p)=?kt
-ln(800-p)=kt + c
800-p=e^(-kt+c)
p=800-e^(-kt+c)=800-c*e^(-kt)

p(0)=500=800-c
c=300

p(2)=700=800-300*e^(-2k)
1/3=e^(-2k)
ln3=2k
k=ln3/2

p(t)=800-300*e^[-(ln3/2)t]=800-300*3^(-t/2)

winnar!