1.

Find the general solution of the differential equation `(dy)/(dx) = log(x+1).`

Answer» We have ,
`(dy)/(dx)=log(x+1)`
`rArr dy=log(x+1)dx`
`rArr int dy = int log(x+1)dx` [integrating both sides]
`rArr y=int {log(x+1)*1}dx + C, ` where C is an arbitrary constant
`={log(x+1)*x}-int(1)/((x+1)) *x dx + C " " `[integrating by parts]
`=x log (x+1) - int ((x+1)-1)/((x+1)) dx + C`
`=x log (x+1) - int {1-(1)/((x+1)) } dx + C`
` = x log (x+1)-x + log(x+1) + C`
`=(x+1)log(x+1)-x+C.`
Hence, `y=(x+1)log(x+1)-x+C` is the required solution.


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