1.

If `x^(y)=e^(x-y)`, prove that `(dy)/(dx)=(logx)/((1+logx)^(2)).`

Answer» We have
`x^(y)=e^(x-y)rArr ylog x=(x-y)`
`rArr (1+logx)y=x`
`rArry=(x)/((1+logx))." …(i)"`
On differentiating both sides of (i) w.r.t. x, we get
`(dy)/(dx)=((1+logx).(d)/(dx)(x)-x.(d)/(dx)(1+logx))/((1+logx)^(2))`
`=((1+logx).1-x.(1)/(x))/((1+logx)^(2))=((1+logx-1))/((1+logx)^(2))=(logx)/((1+logx)^(2)).`


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