Hi, I've found some inappropriate behaviour of the solve function.
>>> x,y = symbols("x y", real=True, nonnegative=True)
>>> solve(y-x**2,x)
[-sqrt(y), sqrt(y)]
The only non-negative case where both sqrt(y) and -sqrt(y) should be
solutions is where y=0, in which case they are equal and not different
after all. It's quite annoying if there should be a single solution of zero!
It should really work like positives:
>>> x,y = symbols("x y", real=True, positive=True)
>>> solve(y-x**2,x)
[sqrt(y)]
I didn't submit an issue because I was not sure if it was deliberate
(perhaps for making floats work properly?).
:L
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