442: Square Root

x² = 81 has two solutions, -9 and 9.

But does √81 have one solution or two? Is it correct to say that √81 = +9 and -9?

Or should we be saying that √81is an expression and that 9, 18/2, 27^(2/3), and 1+6+2, are equivalent expressions?

It is really alarming how often I see materials written by math teachers claiming that for example sqrt(81) is both 9 and -9.
— Kate Nowak (@k8nowak) April 22, 2015