Students deduced that the solution was impossible

[ROBINDESBOIS]

Students deduced that the solution was impossible
to transform it into an impersonal passive
The solution was deduced to be impossible or to have been impossible.
Are both correct'? if so, what ´s the difference in meaning?

[Rusty]

In American English, both passive voice proposals are fine. There is a difference between using 'to be' and 'to have been'. The latter suggests that it was impossible then, but it may be possible now, while the former makes us think that what was impossible then is still impossible now.