Search 80,000+ tutors
Ask a question
0 0

Find the inverse of f(x) = 9x+2 divided by 3x

Tutors, please sign in to answer this question.

1 Answer

Let's start with f(x).
f(x)=(9x+2)/3x  with a domain of all real number except 0.   (we cannot have 0 at the denominator)
In order to find out the inverse, set the function =y, and solve for x
Let's cross multiply (you'll see it more easily if you write it down on paper)
Let's separate the terms that have x's from all the other numbers/variables:
x=-2/(9-3y)      And there you go, the inverse is 9-3y, however.. we generally report the inverse with the same variable so:
f-1(x)=-2/(9-3x)        with a domain of all real numbers except 3. Why 3? the denominator is not allowed to be 0, as we cannot divide by 0.
therefore, 9-3x cannot equal 0, so x cannot equal 3.