Question

Find a formula for the inverse of the function. f(x) = e^6x − 9

Answer 1

Answer:

$f^{-1}(x)=\frac{1}{6}\ln(x+9)$

Step-by-step explanation:

So we have the function:

$f(x)=e^{6x}-9$

To solve for the inverse of a function, change f(x) and x, change the f(x) to f⁻¹(x), and solve for it. Therefore:

$x=e^{6f^{-1}(x)}-9$

Add 9 to both sides:

$x+9=e^{6f^{-1}(x)}$

Take the natural log of both sides:

$\ln(x+9)=\ln(e^{6f^{-1}(x)})$

The right side cancels:

$\ln(x+9)=6f^{-1}(x)$

Divide both sides by 6:

$f^{-1}(x)=\frac{1}{6}\ln(x+9)$

And we're done!