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October 10th, 2015, 02:58 AM  #1 
Newbie Joined: Sep 2015 From: AU Posts: 5 Thanks: 0  Second order diff question (plz help)
How do i approach this question?? http://imgur.com/iZUS77u http://imgur.com/wncJkrT I got a) as my" + By' =mg however can't solve for part b) Any help would be greatly appreciated!! Thank you！！！！！ Last edited by mikehepro; October 10th, 2015 at 03:00 AM. 
October 10th, 2015, 03:10 AM  #2  
Math Team Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902  Quote:
Now we look for a single function that satisfies the entire equation. The right hand side, mg, is a constant so, normally, we would try a constant function, A. But a constant function is already a solution so instead we try y= At. Perhaps that was where you had the difficulty. Then y'= A and y''= 0 so the equation m(0)+ BA= mg so that A= mg/B. The general solution to the entire equation is $\displaystyle y(t)= C_1+ C_2e^{\frac{B}{m}t}+ \frac{mg}{B}$.  
October 10th, 2015, 05:24 AM  #3 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,671 Thanks: 2651 Math Focus: Mainly analysis and algebra 
There's a $\displaystyle t$ missing from the final term.


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