Thread: Inverse function

Find the inverse function for f (x) = 5x over x + 3 in the form of y = f to the power of - 1 (x)

How would I work this out anyone?

Originally Posted by mathsgirl123431

Find the inverse function for f (x) = 5x over x + 3 in the form of y = f to the power of - 1 (x)
How would I work this out anyone?

Solve for in .
Then

is that the answer or is there more to do after that? i've never done these before! thanks for replying

Originally Posted by mathsgirl123431

is that the answer or is there more to do after that? i've never done these before! thanks for replying

NO You solve for . When you do that you get , function of .

Then set

Originally Posted by mathsgirl123431

is that the answer or is there more to do after that? i've never done these before! thanks for replying

Plato told you what to do. You still have to do it yourself! (Do you know the definition of "inverse function". You might want to compare that to what Plato told you.

Sorry guys, okay well this is what I tried myself:


y = 5x/(x + 3)

Next, switch the x and y variables, and re-write the function as:

x = 5y/(y + 3)

Now, solve this equation for y:

x(y + 3) = 5y

xy + 3x = 5y

3x = 5y - xy

3x = y(5 - x)

y = 3x / (5 - x)


Solution: f^-1(x) = 3x / (5 - x)



Thanks for the advice, I did work it out right didn't I?