(r0q)(1)=? (q0r)(1)=?

  • Thread starter nate1936
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  • #1
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Homework Statement


This problem is giving me issues, mainly because of how it is set up.


Homework Equations


Here is a picture of what my problem is,
http://img23.imageshack.us/img23/1723/heko.png [Broken]


The Attempt at a Solution


I am attempting to solve this problem, and I haven't encountered anything like it in the book so far, I'm assuming I take the variables "q of x" and "r of x", but when solving, why are they swapped around? Is the (r0q)(1)= and (q0r)(1)= representing multiplication? I haven't seen that raised circle in the middle before. I'm assuming it has something to do with logarithms? I don't need anyone to show me how this particular problem is solved, [that would be cheating though it doesn't really matter to much in this class, 90% of the grade is based on the test]

If someone could change the variables and numbers, and/or just go through the steps on how I should go about solving this type of problem, I would really appreciate it.
 
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Answers and Replies

  • #2
768
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Well this is the composition of functions, which is not commutative. That mean qor (using o as the symbol of composition for lack of a better button) does not necessarily equal roq.

Do you know how to find q of r, ignoring the 1 for now?
 
  • #3
HallsofIvy
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The crucial point is, do you know the definition of "[itex]f\circ g(x)[/itex]"? This is known as the "composition of functions". If this is the first course in which you have seen it, I'll bet there's a definition in the same section of the book in which the problem occurs!
 
  • #4
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Thank you for your help so far, because I now know it is a "Composition of functions" problem I was able to find out how to get started with this I think.
r o q (1) can be re-written as (r(q(1)) from here, can I have a hint as to what the next step is?
If the (1) were an x I would substitute in the variables and solve for x, however I'm not sure what to do with the (1)
 
  • #5
768
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You can find q(1) first and then use that in r(x), or you can first find q of r as if you only had an x, and then substitute the 1 in the final step. Try both, you should get the same answer both times.
 
  • #6
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Is there a special function you are talking about when you say find q(1) [in the first way to solve it you have posted] or are you just multiplying the q (x) variable times one?

Sorry for my stupid questions, I have to figure this out somehow though!
 
  • #7
SammyS
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Is there a special function you are talking about when you say find q(1) [in the first way to solve it you have posted] or are you just multiplying the q (x) variable times one?

Sorry for my stupid questions, I have to figure this out somehow though!
To find q(1), substitute 1 in for the x that is given in the definition of q(x).

[itex]q(x)=x^2+3[/itex]
 
  • #8
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edit: nevermind I found a forum with much more straightforward answers. Thanks anyway
 
  • #9
HallsofIvy
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Did you find a forum that will take your tests for you? Getting the answer to homework problems from others, rather than working them out for yourself is a sure way to fail a course.
 
  • #10
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Actually I found a forum that instead of side tracking and telling me what I already know, actually showed me an example problem, and showed me the steps required to solve this type of problem. I learn in a different way than the community involved on this board apparently. Sorry if that offends you.
 
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