Answer:
x = -13 or x = 1
Step-by-step explanation:
(x+6)^2 is x^2+12x+36
(x+6)^2-49 is x^2+12x-13, looks hard to factor.
BUT (x+6)^2 - 49 is the difference of two squares, so the factorization is
(x+6+7)(x+6-7) = (x+13)(x-1),
which is factorization of x^2+12x-13.
The expression is zero when either factor is zero, x = -13 or x = 1
Check: f(x) = (x+6)^2-49
f(-13) = (-13+6)^2-49 = (-7)^2-49 = 0
f(1) = (1+6)^2-49 = (7)^2-49 = 0