+118723 I have edited this answer - my original answer was incorrect. Thanks for notifying me Chris :))
The square root of 28 is between sqrt of 25 and sqrt of 36 So it is between 5 and 6
so the NEGATIVE square root od 28 is between -sqrt25 and -sqrt36. SO it is between -6 and -5
I put the -6 first because it is smaller than -5 
The largest integer that is less than a number between -6 and -5 is -6
