February 8th, 2013, 06:15 AM  #1 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  mathematics  Q 8
Hi can please check my answer for a and b 
February 8th, 2013, 06:50 AM  #2 
Math Team Joined: Sep 2007 Posts: 2,409 Thanks: 6  Re: mathematics  Q 8
(B) is correct. For (A) you have Surely, you understand that y' on the left is wrong? From you get but NOT y'= 0. Differentiating again, ^2 2yy'' 2cy''= 0" />. Now, going back to ou can get so that . Replace the "c" in with . 
February 8th, 2013, 10:19 AM  #3 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: mathematics  Q 8
can explain to me line number 4 and 5 from where you got 2(y)^2 in line 4 
February 9th, 2013, 02:39 PM  #4 
Math Team Joined: Sep 2007 Posts: 2,409 Thanks: 6  Re: mathematics  Q 8
It's the product rule. We start with The derivative of 2x, with respect to x, is, of course, 2. The derivative of 2yy' is (y'+ 2(y)(y''= 2y'^2+ 2yy''" />. The derivative of 2xy' is y'+ 2x(y''= 2y'+ 2xy''" />. Putting those together, the derivative of is .


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