Applied DE

Printable View

August 16th 2011, 07:28 AM
decoy808

Applied DE

Need help with a past exam questions for revision. could someone help me with the method for the questions or hint at what I need to do. many thanks

http://i56.tinypic.com/2wfrez7.jpg

http://i56.tinypic.com/2zsutm0.jpg
August 16th 2011, 07:52 AM
Prove It

Re: Applied DE

Well for (i), if $\displaystyle \frac{dy}{dt}$ is proportional to the product of $\displaystyle x$ and $\displaystyle y$ , then

$\displaystyle \frac{dy}{dx} = kxy = k\left[\frac{10}{(1 + t)^3}\right]y$ where $\displaystyle k$ is some constant.

Now use the fact that when $\displaystyle t = 0, y = 20$ and $\displaystyle \frac{dy}{dt} = -40$ to find $\displaystyle k$ .

All times are GMT -8. The time now is 05:17 PM.

Copyright © 2005-2013 Math Help Forum. All rights reserved.

Copyright © 2005-2013 Math Help Forum. All rights reserved.