Question 285425

let's say u= (x-5)
u^2-6u+8
factors are -4 and -2
(u-4)*(u-2)
now substitute x-5 for u
(x-5-4)*(x-5-2)
(x-9)*(x-7)
Which works.
I can't for the life of me think how you got (x-11) and (x+3).

if you had calculated out the original expression you should have gotten 
x^2-16x+63
which also factors to (x-9)(x-7)