x^2 - 16x + 56 = 0
= (x - 8)^2 - 64 +56= 0
= (x - 8)^2 - 8 = 0
x^2 - 8x + 11 = 0
(x - 4)^2 - 16 + 11
(x - 4)^2 - 5 = 0
(x + 15)(x + 5) = 96
x^2 + 20x + 75 = 96
(x + 10)^2 - 100 + 75 = 96
(x + 10)^2 = 96 +25 = 121
taking square roots:-
x + 10 = 11
x = 1