f-1(3) when f(x) = 2 x minus 7, all over 3

Question

anonymous · Answer

$\sf \large f(x) = \frac{2x-7}{3}$

to get the inverse:

1. Let f(x)= y, so it will be like :  $\sf \large y = \frac{2x-7}{3}$

2. Switch the places of x and y variables:   $\sf \large x= \frac{2y-7}{3}$

3. Solve the equation in terms of y. Tell me what will you get.

4.Change y into $\sf f(x)^{-1}$

5. Solve $\sf f(3)^{-1}$ by substituting x=3. Tell me also what will you get in this part.

anonymous · Answer

How do I solve it? I'm confused

anonymous · Answer

hmm.. let's start with the first step. you just have to replace f(x) with y to make things easier :) is this part clear?

anonymous · Answer

Yes I understand that part its solving $$2y - 7 \over 3$$ that I don't get how to do.

anonymous · Answer

ahh okay great. 

so you have: |dw:1429798984089:dw|

anonymous · Answer

well i tired it and got 
$$3x + 7 \over 2 $$

anonymous · Answer

which would = y

anonymous · Answer

alright let's see :)
|dw:1429799669937:dw|

That's perfect! good job :D

so you're done with step 3.
I'll do step 4 for you.
Replace y into f(x)^-1
$\sf \Large f(x)^{-1}= \frac {3x + 7}{ 2}$

Now, the final step :)
subsitute x= 3 in the equation and simplify!