Using the quadratic formula gives:
1,2=−1±√12−4⋅7(−5)2⋅7
x1=−1+√1412⋅7,x2=−1−√1412⋅7
x=−1+√14114,x=−1−√14114
So if a and b are roots:
(−1+√14114−4)(−1−√14114−4)
(EDIT: Just you are calc if you don't know how to solve!!!)
Just solve that and you got the answer 
-Vinculum