Combining functions - just another check

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Discussion Overview

The discussion revolves around the composition of functions, specifically the functions f(x) = 2/x and g(x) = x/x+2. Participants are checking the correctness of the composition and exploring the implications for the domain of the resulting function.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents the composition of functions as fog = f(g(x)) and provides an initial calculation.
  • Another participant suggests that the last two equations need to be rechecked, proposing that the correct expression should be 2*(x+2)/x.
  • A different participant emphasizes the importance of using parentheses and considering the domain of both functions, questioning what values of x are excluded.
  • A participant acknowledges a mistake in their calculation regarding distribution and expresses uncertainty about how to find the domain.
  • Another participant clarifies that the domain consists of the values for which f(x) and g(x) are undefined, indicating these values will be excluded from the domain.
  • One participant asserts that the domain should be specified for a function to be properly defined, critiquing the lack of emphasis on this in educational materials.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the initial calculations and the importance of defining the domain. There is no consensus on the correct expression for the composition or the approach to determining the domain.

Contextual Notes

Participants highlight the need for clarity in mathematical expressions and the significance of domain considerations, but specific assumptions and definitions remain unresolved.

Who May Find This Useful

Individuals interested in function composition, mathematical reasoning, and domain analysis may find this discussion relevant.

Agent_J
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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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Better recheck the last two equations.
2*(x+2)/x is what you meant, is it not?
 
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?).
 
oh ya, I forgot to distribute the 2

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

cookiemonster
 
The domain should be given otherwise it isnt' a function. At some point teachers and basic textbook writers are going to learn this.
 

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