Purgatory 0 Posted February 27, 2013 Share Posted February 27, 2013 Hi. I am struggling to understand what I am doing wrong with this equation. They ask for the general solution and then the particular solution afterwards. Given x(dy/dx) + 5y = 7x^2 , y(2)=5 => dy/dx + (5/x)y = 7x integrating factor: e^integral(5/x) = e^(5lnx) = x^5 multiply by this gives: x^5(dy/dx)+(5/x)y(x^5)= 7x^6 => Dx[(x^5)(y)]= 7x^6 integrate both sides => (x^5)(y)= x^7 + C => y(x)= x^2 + C/(x^5) (divided by x^5) ok thats the general solution Now I get the particular solution by subin in (2,5) so 5 = 4 + C/32 so C = 32 sub in and you have an answer... The answer they give is y(x)= (x+4x^-2) It makes no sense in my head.. If anyone could confirm my answer it would be appreciated. Link to post Share on other sites

Crimson Sunbird 1 Posted March 1, 2013 Share Posted March 1, 2013 Your solution looks fine to me. Link to post Share on other sites

x(x-y) 10 Posted March 1, 2013 Share Posted March 1, 2013 Yeah, your answer seems to be correct - looks like an error in your textbook. Link to post Share on other sites

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