I assume this goes here ;)

Been a long while since I posted a problem :p the difficulty level has probably gone up loads since last year xD (which happens if your forced to take 2 years of math in a week :p) Anyway, I had theoretical math this morning and suddenly the professor started babbling something like...

is a root out of

if

I had the basics of complex numbers taught at a very fast pace this summer, but I haven't seen roots of complex numbers... So I asked the professor if she could elaborate on the meanings of the various symbols that suddenly popped up and she wouldn't because I'm supposed to know basic math. So could anyone elaborate a bit on the meaning of

? As I can't find anything about them in my high school notes... Thanks ^^