The function g(x)=8(4x) is reflected across the x-axis to create f(x). On a coordinate plane, 2 exponential functions are shown. Function f (x) approaches y = 0 in quadrant 3 and decreases into quadrant 4. It crosses the y-axis at (0, negative 8). Function g (x) approaches y = 0 in quadrant 2 and increases into quadrant 1. It crosses the y-axis at (0, 8).

What is the equation of f(x)?