Finding the inverse of a log role is as straightforward as complying with the suggested steps below. You will realize later after seeing some instances that most of the job-related boils under to solving an equation. The vital steps associated include isolating the log expression and also then rewriting the log in equation right into an exponential equation. You will view what I average when you walk over the worked instances below.

You are watching: How to find the inverse of a log function

Steps to uncover the train station of a Logarithm

STEP 1: change the function notation f\left( x \right) by y.

f\left( x \right) \to y

STEP 2: move the roles of x and also y.

x \to y

y \to x

STEP 3: isolate the log in expression on one side (left or right) that the equation.


STEP 4: transform or change the log in equation right into its identical exponential equation.

Notice the the subscript b in the \log type becomes the base v exponent N in exponential form.The change M continues to be in the very same place.

STEP 5: deal with the exponential equation for y to acquire the inverse. Then replace y by f^ - 1\left( x \right) i beg your pardon is the station notation to compose the last answer.

Rewrite \colorbluey as \colorredf^ - 1\left( x \right)

Examples of how to uncover the inverse of a Logarithm

Example 1: uncover the train station of the log in equation below.

f\left( x \right) = \log _2\left( x + 3 \right)

Start by instead of the duty notation f\left( x \right) through y. Then, interchange the functions of \colorredx and \colorredy.


Proceed by resolving for y and also replacing the by f^ - 1\left( x \right) to get the inverse. Part of the solution listed below includes rewriting the log equation into an exponential equation. Here’s the formula again the is provided in the counter process.

Notice how the base 2 the the log expression i do not care the base with an exponent the x. The stuff inside the parenthesis stays in its original location.

Once the log expression is gone by converting it right into an exponential expression, we can finish this turn off by individually both political parties by 3. Don’t forget to change the change y by the inverse notation f^ - 1\left( x \right) the end.


One method to check if we gained the exactly inverse is to graph both the log equation and inverse duty in a single xy-axis. If your graphs room symmetrical along the heat \large\colorgreeny = x, then we have the right to be confident that our prize is without doubt correct.

Example 2: find the station of the log function

f\left( x \right) = \log _5\left( 2x - 1 \right) - 7

Let’s add up some level of challenge to this problem. The equation has actually a log expression gift subtracted by 7. I hope you can assess the this difficulty is exceptionally doable. The solution will be a little bit messy but definitely manageable.

So I start by transforming the f\left( x \right) right into y, and swapping the roles of \colorredx and \colorredy.

Now, we have the right to solve for y. Include both sides of the equation through 7 to isolation the logarithmic expression ~ above the best side.

By efficiently isolating the log in expression on the right, we are ready to transform this right into an exponential equation. Observe that the basic of log expression i beg your pardon is 6 becomes the basic of the exponential expression on the left side. The expression 2y-1 within the parenthesis ~ above the best is now by itself without the log in operation.

After act so, continue by addressing for \colorredy to attain the required inverse function. Do that by including both sides by 1, complied with by splitting both political parties by the coefficient the \colorredy i m sorry is 2.

Let’s sketch the graphs of the log and also inverse features in the very same Cartesian plane to verify that they are certainly symmetrical along the line \large\colorgreeny=x.

Example 3: uncover the station of the log in function

So this is a little an ext interesting 보다 the an initial two problems. Observe that the base of log expression is missing. If you encounter something favor this, the presumption is that we room working through a logarithmic expression with base 10. Always remember this concept to aid you get about problems v the same setup.

I expect you space already more comfortable through the procedures. We begin again by do f\left( x \right) together y, climate switching roughly the variables \colorredx and also \colorredy in the equation.

Our following goal is to isolate the log expression. We have the right to do the by individually both sides by 1 adhered to by splitting both sides by -3.

The log in expression is currently by itself. Remember, the “missing” base in the log in expression implies a base of 10. Change this into an exponential equation, and also start resolving for y.

Notice the the whole expression on the left side of the equation becomes the exponent of 10 i beg your pardon is the implied basic as stated before.

See more: How To Find The Constant Of Variation : Definition & Example

Continue solving for y by subtracting both sides by 1 and also dividing through -4. After ~ y is fully isolated, replace that through the inverse notation \large\colorbluef^ - 1\left( x \right). Done!

Graphing the original function and its inverse on the exact same xy-axis reveals the they space symmetrical about the heat \large\colorgreeny=x.

You might also be interested in:

Inverse that a 2×2 Matrix

Inverse that Absolute value Function

Inverse of consistent Function

Inverse of Exponential Function

Inverse of straight Function

Inverse the Quadratic Function

Inverse of rational Function

Inverse the Square root Function

ABOUTAbout MeSitemapContact MePrivacy PolicyCookie PolicyTerms that Service
MATH SUBJECTSIntroductory AlgebraIntermediate AlgebraAdvanced AlgebraAlgebra indigenous ProblemsGeometryIntro come Number TheoryBasic math Proofs
CONNECT through US
We usage cookies to offer you the ideal experience on our website. You re welcome click yes sir or Scroll under to usage this website with cookies. Otherwise, check your web browser settings to turn cookies off or discontinue utilizing the site.OK!Cookie Policy