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][]
And the result showed,
ConditionalExpression[1 - E^-y, -\[Pi] <= Im[y] < \[Pi]]