If x + y = 15 and xy = 14, then the value of x - y is  :

11 12 14 13

13

If x + y  = n then, x - y  = \(\sqrt {n^2 - 4xy}\) If x + y = 15 xy = 14, then the value of x - y i= \(\sqrt {15^2 - 4(14)}\)  x - y i= \(\sqrt {169}\) = 13