State the interval where g(x)> f(x)

The interval where g(x) > f(x) is (-∞,2)

the difference of two squares is a special form that has a factorization worth memorizing.

a² - b² = (a - b)(a + b)

your equation can be factored as

x² - 16 = 0

(x - 4)(x + 4) = 0

the zero product rule tells you the solutions are the values of x that make these factors zero: x=4, x=-4.