Hello!

I need help to solve this:

If F( ( x + 3 ) / ( x + 1 ) ) = 3x + 2 x belongs to R \ {!-1}

then F( 5 ) = ?

It is a first time ever for me to have met this kind of problems and functions in general (I'm trying to teach myself math to get on university), I have very weak background in math so you can imagine my struggle.

I tried to do something like this:

x = 1

F( ( 1 + 3 ) / ( 1 + 1 ) ) = 3 * 1 + 2

F( 4 / 2 ) = 5

so, I have now 4/2 and 5 and I say F(4/2) = 5

and to find F(5) I did this: first I found by how much I need to multiply 4/2 to get 5:

4/2 * y = 5

y = 5 * (2/4)

y = 10/4

y = 5/2

now, I know that in order to get the value of F(5) I need to divide y with f(4/2):

f(4/2) = 5

so, y / 5 = 5/2 * 1/5 = 1/2 --- and the book states that is the right answer, BUT when I used for x some other number, like 3, I didn't get that answer. Please help.