# I need help with 1 question. VERY PLEASE!

I need help with 1 question. VERY URGENT PLEASE!

## Homework Statement

if F[g(x)] = R(x) where g(x) and r(x) is known find f(x).

none

## The Attempt at a Solution

I did it but i dont know if it is right:

(g^-1 of x) = x

so...

F(x) = r(g^-1 of x)

f(x)=R(x)/g(x)

f(x)=R(x)/g(x)

how did u get that?

Well I'm not 100% certain its that but I just used logic. Division is the inverse of multiplication so if f[g(x)]=R(x) then f(x)=R(x)/g(x). i.e. f[g(2)]=12 then f(x)=12/2. 12/2=6 and 6(2)=12

Dick
Homework Helper
Well I'm not 100% certain its that but I just used logic. Division is the inverse of multiplication so if f[g(x)]=R(x) then f(x)=R(x)/g(x). i.e. f[g(2)]=12 then f(x)=12/2. 12/2=6 and 6(2)=12

It's not multiplication. It's composition of functions. And assuming g is invertible then the OP is correct. Except don't say g^(-1)(x)=x. That's ridiculous. g(g^(-1)(x))=x.

Last edited:
EnumaElish
Homework Helper
Isn't the OP correct only if F(g) = g(F) and R(g) = g(R) ?

Dick