Combining functions - just another check

  • Thread starter Agent_J
  • Start date
  • #1
13
0
combining functions - just another check :)

f(x) = 2/x
g(x) = x/x+2

fog = f(g(x))
= f(x/x+2)
=2/x/x+2
=2 * x+2/x
=2x+2/x

[Edit (by ahrkron): no changes; took back my edit (I meant to reply)... the post is now in its original form]
 
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Answers and Replies

  • #2
Better recheck the last two equations.
2*(x+2)/x is what you meant, is it not?
 
  • #3
ahrkron
Staff Emeritus
Gold Member
736
1
Be careful. Use parentheses, and you most probably need to think about the domain of both functions (what values of x are excluded on each case? what about the composition?).
 
  • #4
13
0
oh ya, I forgot to distribute the 2

how would I find the domain ahrkron :redface:
 
  • #5
For what values of x are f(x) and g(x) undefined? Those will be out of the domain.

cookiemonster
 
  • #6
matt grime
Science Advisor
Homework Helper
9,395
3
The domain should be given otherwise it isnt' a function. At some point teachers and basic text book writers are going to learn this.
 

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