If f(x) = ln 4x, what is the value of f^-1(6). (The f raises to the -1 is the inverse function of f(x).
The answer is 100.86.
The natural log (ln) has a base e, so another way of rewriting f(x) = ln 4x or y = ln 4x:
$\displaystyle e^{y} = 4x$
$\displaystyle \frac{e^{y}}{4} = x$
y = 6. Substituting it into this equation and solving for x will yield approximately 100.86.