1.

If `e^x + e^(f(x)) = e` then domain of f(x) isA. `(-oo, 1)`B. `(-oo, 0)`C. `(1, oo)`D. none of these

Answer» Correct Answer - A
We have,
`e^(x) + e^(f(x)) = e`
`rArr e^(f(x)) = e-e^(x)`
`rArr f(x) = log_(e) (e-e^(x))`
`rArr f(x) = log_(e) e+ log_(e) (1-e^(x-1))`
`rArr f(x) = 1+ log_(e) (1-e^(x-1))`
Clearly, for (f) to be real, we must have
`1-e^(x-1) gt 0 rArr e^(x) lt e rArr x lt 1 rArr x in (-oo,1)`


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