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Let f(x)=x^(3),x in (0,oo) and let g(x) ...

Let `f(x)=x^(3),x in (0,oo)` and let g(x) be inverse of f(x), then g'(x) must be

A

`x(1+log x)`

B

`x(1+ log (x))`

C

`(1)/(x(1+log g(x))`

D

non-existent

Text Solution

Verified by Experts

`f(x)=x^(x),g(x)" is inverse of "f(x)`
`therefore" "f(g(x))=x`
`rArr" "f'(g(x))cdotg'(x)=1`
`rArr" "g'(x)=(1)/(f'(g(x)))`
`"Now "log_(e)f(x)=xlog_(e)x`
`therefore" "(f'(x))/(f(x))=x(1)/(x)+log_(e)x=1+log_(e)x`
`therefore" "f'(x)=x^(x)(1+log_(e)x)`
`therefore" "f'(g(x))=(g(x))^(g(x))(1+log g(x))`
`"Now "f(g(x))=g(x)^(g(x))=x`
`therefore" "f'(g(x))=x(1+log g(x))`
`therefore" "g'(x)=(1)/(x(1+log g(x)))`
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