Finding the train station of a log role is as straightforward as adhering to the suggested steps below. You will realize later after see some examples that most of the work-related boils down to fixing an equation. The vital steps connected include isolating the log expression and then rewriting the log in equation into an exponential equation. You will check out what I average when you go over the worked instances below.

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

Steps to discover the train station of a Logarithm

STEP 1: replace the function notation fleft( x ight) by y.

fleft( x ight) o y

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

x o y

y o x

STEP 3: isolate the log in expression top top one next (left or right) the the equation.


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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 through exponent N in exponential form.The change M stays in the very same place.

STEP 5: settle the exponential equation for y to obtain the inverse. Then change y through f^ - 1left( x ight) i m sorry is the station notation to write the final answer.

Rewrite colorbluey as colorredf^ - 1left( x ight)

Examples of how to find the inverse of a Logarithm

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

fleft( x ight) = log _2left( x + 3 ight)

Start by replacing the role notation fleft( x ight) through y. Then, interchange the duties of colorredx and also colorredy.


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



Notice exactly how the basic 2 that the log in expression becomes the base with an exponent that x. The stuff within the parenthesis remains in its initial location.

Once the log in expression is unable to do by converting it into an exponential expression, us can finish this turn off by subtracting both sides by 3. Don’t forget to replace the variable y through the station notation f^ - 1left( x ight) the end.


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One way to check if we got the exactly inverse is come graph both the log in equation and inverse duty in a single xy-axis. If your graphs room symmetrical follow me the heat largecolorgreeny = x, then we have the right to be confident the our price is without doubt correct.


Example 2: discover the train station of the log function

fleft( x ight) = log _5left( 2x - 1 ight) - 7

Let’s add up some level of an obstacle to this problem. The equation has actually a log expression gift subtracted by 7. I hope you can assess that this difficulty is incredibly doable. The systems will it is in a little messy but definitely manageable.

So I begin by changing the fleft( x ight) right into y, and swapping the duties of colorredx and also colorredy.


Now, we can solve because that y. Add both sides of the equation by 7 to isolation the logarithmic expression top top the right side.


By properly isolating the log in expression ~ above the right, us are all set to transform this into an exponential equation. Observe that the basic of log in expression i beg your pardon is 6 i do not care the base of the exponential expression ~ above the left side. The expression 2y-1 within the parenthesis ~ above the right is currently by chin without the log in operation.

After law so, continue by fixing for colorredy to acquire the forced inverse function. Do that by including both political parties by 1, adhered to by dividing both sides by the coefficient the colorredy i beg your pardon is 2.


Let’s sketch the graphs the the log and also inverse attributes in the very same Cartesian airplane to verify that they are without doubt symmetrical follow me the heat largecolorgreeny=x.


Example 3: find the inverse of the log in function


So this is a little an ext interesting than the an initial two problems. Observe that the basic of log in expression is missing. If you conference something like this, the assumption is the we room working with a logarithmic expression through base 10. Always remember this concept to aid you get approximately problems through the very same setup.

I hope you space already more comfortable with the procedures. We begin again by do fleft( x ight) as y, climate switching around the variables colorredx and colorredy in the equation.


Our next goal is to isolation the log expression. We have the right to do that by subtracting both political parties by 1 complied with by separating both political parties by -3.


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

Notice the the entire expression ~ above the left side of the equation becomes the exponent of 10 i beg your pardon is the implied base as stated before.

See more: What Is The Purpose Of Spindle Fibers : Definition, Location & Purpose

Continue fixing for y by individually both sides by 1 and also dividing by -4. After y is fully isolated, replace that through the station notation largecolorbluef^ - 1left( x ight). Done!


Graphing the original duty and its train station on the exact same xy-axis reveals the they room symmetrical about the line largecolorgreeny=x.


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