Respuesta :

x = 16
x = - 16

You could do it this way
x^2 - 256 = 0
(x - 16)(x + 16) = 0
x - 16 = 0
x = 16

x + 16 = 0
x  = - 16

x² = 256
x = 
±√256
x = ±16

 the solutions are x = -16 and x = 16