Answer:
x = -6 or x = 6
Explanation:
2x^2 - 72 = 0
Divide both sides by 2.
x^2 - 36 = 0
Factor the left side. It is a difference of two squares. The pattern for that is
a^2 - b^2 = (a + b)(a - b). Now we apply that pattern to x^2 - 36 on the left side.
(x + 6)(x - 6) = 0
x + 6 = 0 or x - 6 = 0
x = -6 or x = 6