My mistake, I wrote Sqrt[2]
rather than Sqrt[10]
;-)
So I should have written
(x-Sqrt[10])(x+Sqrt[10])
I just edited my original post to correct this....
I do not believe that there is a way to enter the plus/minus character into Wolfram|Alpha. But when, in algebra, one uses that character it is just a shorthand for writing both cases.
I also note that one would hope that Wolfram|Alpha would give the answer to the statement
quadratic equation with roots 3 and 9
and give
27 - 12 x + x^2
as the result. But apparently the Wolfram|Alpha parser does note recognize this. I sent in a suggestion that it should address this case.