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Differential Equations

Question
CBSEENMA12035921

Find the general solution of the differential equation,

x log x dydx + y = 2x log x

Solution

x log x dydx + y = 2x log x

Dividing all the terms of the equation by  x log x, we get

 dydx + yx log x = 2x2

This equation is in the form of a linear differential equation

dydx + py = Q,   where   P = 1x log x  and  Q = 2x2Now, I.F = e pdx =  e 1x log x dx = e log ( log x ) = log x

The general solution of the given differential equation is given by 

y x I.F. =  ( Q x I.F. ) dx + C

y log x =   2x2 log x  dxy log x = 2 log x ×1x2  dx.               = 2  log x ×  1x2 dx -  ddx  log x  × 1x2 dx  dx                = 2  log x  - 1x  -   1x ×  -1x   dx                = 2  - log xx +  1x2 dx                 = 2  - log xx - 1x  + CSo the required general solution is    y log x = - 2x  1 + log x  + C

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