Posted by **Ashley** on Sunday, April 7, 2013 at 10:17pm.

Given f(x)=-4+lnx; Find the inverse of f. f^-1=?

- Algebra -
**Reiny**, Sunday, April 7, 2013 at 11:08pm
original:

y = 4 + lnx

inverse:

x = 4 + lny

solving for y

lny = x-4

y = e^(x-4)

f^-1 (x) = e^(x-4)

- Algebra -
**Kendall**, Sunday, April 7, 2013 at 11:23pm
How do you find the domain and range?

- Algebra -
**Reiny**, Sunday, April 7, 2013 at 11:31pm
domain is your choice of x's that you can use in your equation

For logs, one of the main properties is that I can only take the log of a positive number

so for y = 4 + lnx , the domain is x > 0

however, the result of taking such logs results in any real number, so the range is y ∈ R

After taking the inverse of a function, the domain of the original becomes the range of the inverse, and the range of the original becomes the domain of the inverse.

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