Find the domain of the function (f/g)(x), given f(x) = x² - 4x - 21 and g(x) = x² - 16.

{x | x ≠ -4 and x ≠ 4}
{x | x ≠ -3 and x ≠ 7}
{x | x ≠ 4}

I have tried photo math and such and can not get an answer

Thanks