Finding the inverse of a log role is as basic as adhering to the said steps below. You will realize later after see some examples that many of the job-related boils down to addressing an equation. The an essential steps affiliated include isolating the log in expression and then rewriting the log in equation right into an exponential equation. Friend will view what I median when you walk over the worked examples below.

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

## Steps to find the inverse of a Logarithm

STEP 1: replace the role notation f\left( x \right) by y.

f\left( x \right) \to y

STEP 2: switch the functions of x and also y.

x \to y

y \to x

STEP 3: isolate the log in expression ~ above one side (left or right) of the equation.

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

Notice the the subscript b in the \log type becomes the base through exponent N in exponential form.The variable M remains in the same place.STEP 5: fix the exponential equation for y to gain the inverse. Then replace y by f^ - 1\left( x \right) i beg your pardon is the train station notation to create the last answer.

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

### Examples of just how to uncover the inverse of a Logarithm

**Example 1:** discover the station of the log in equation below.

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

Start by replacing the duty notation f\left( x \right) by y. Then, interchange the roles of \colorredx and also \colorredy.

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

Notice how the base 2 of the log expression i do not care the base v an exponent the x. The stuff inside the parenthesis continues to be in its original location.

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

One means to check if we obtained the correct inverse is come graph both the log equation and also inverse function in a solitary xy-axis. If your graphs room symmetrical follow me the line \large\colorgreeny = x, climate we have the right to be confident the our answer is without doubt correct.

**Example 2:** uncover the station of the log function

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

Let’s add up part level of difficulty to this problem. The equation has a log in expression gift subtracted by 7. I hope you deserve to assess the this trouble is exceptionally doable. The equipment will it is in a bit messy however definitely manageable.

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

Now, we can solve for y. Include both sides of the equation through 7 to isolate the logarithmic expression on the ideal side.

By successfully isolating the log in expression on the right, we are all set to convert this into an exponential equation. Observe that the basic of log expression which is 6 becomes the base of the exponential expression top top the left side. The expression 2y-1 inside the parenthesis on the ideal is currently by itself without the log in operation.

After act so, proceed by resolving for \colorredy to achieve the forced inverse function. Perform that by adding both political parties by 1, adhered to by separating both sides by the coefficient the \colorredy which is 2.

Let’s sketch the graphs the the log and also inverse functions in the same Cartesian aircraft to verify the they are undoubtedly symmetrical follow me the heat \large\colorgreeny=x.

**Example 3:** discover the station of the log in function

So this is a little more interesting than the first two problems. Observe the the basic of log expression is missing. If you conference something like this, the presumption is that we are working v a logarithmic expression v base 10. Constantly remember this principle to assist you get roughly problems through the same setup.

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

Our next goal is to isolate the log in expression. We deserve to do that by individually both political parties by 1 complied with by splitting both sides by -3.

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

Notice the the whole expression on the left next of the equation i do not care the exponent the 10 i m sorry is the implied base as discussed before.

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Continue resolving for y by individually both political parties by 1 and dividing by -4. After ~ y is totally isolated, change that by the inverse notation \large\colorbluef^ - 1\left( x \right). Done!

Graphing the original function and its train station on the same xy-axis reveals the they are symmetrical around the line \large\colorgreeny=x.

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