√H = o
Uh,you're treating it as a variable but if you find the value of H(say 9) then take it's root you would get two solutions(±3).
For H = 9:
o = √9
o = 3
Compare that to what could have been written, but wasn't:
±√H = o
o = ±√9
o = ±3
Does this look familiar?
The root symbol never(in my experience) has a ± in front of it because the signs are taken only when a number is obtained not while it's still a variable.
See also http://mathforum.org...view/70486.html.