Respuesta :

4x^2 - 36 = 0
4x^2 = 36
x^2 = 9
x = 3 or -3
the answer is C
It is short work to check the answer choices.
  4*3² -36 = 0 . . . . yes, so +3 is a solution
  4*(-3)² -36 = 0 . . . . yes, so -3 is a solution

The appropriate choice is ...
  C. {-3, 3}