# Condition at Inverse function

My goal is to get inverse of -Log[1 - x]. But the result shows conditional expression. Could I know Why the condition -[Pi] <= Im[y] < [Pi] shows? There wass no assumption at variable y.

u[x_] := -Log[1 - x]

x /. Solve[y == u[x], x][[1]]


And the result showed,

ConditionalExpression[1 - E^-y, -\[Pi] <= Im[y] < \[Pi]]

• Since x or y can be a complex number. InverseFunction[u] Mar 24 at 12:35
• Thank you for reply. but I wonder How to remove the conditions(= Is there a way to assume x and y as Real at Mathmatica for this case?)
– Soon
Mar 24 at 13:51

u[x_] := -Log[1 - x]

1 - E^-y