a+b=﹣11,ab=16
(a-b)²=(a+b)²-4ab=121-64=57
根号下(a除以b)减根号下(b除以a)
=根号下(a除以b)减根号下(b除以a)
=(a-b)÷根号ab
=±√57÷4
=±√57/4