injective function and image - XP Math - Forums

 XP Math - Forums injective function and image

 10-31-2009 #1 LeroyTsruya   Join Date: Oct 2009 Posts: 1 injective function and image Hi all! i have a problem solving this: given the function g: R->R g(x) = (2x^2 - x)/(3x^2 +x + 1) I have to determine g is an injective function, and also find its image. any ideas? Thanks!
11-01-2009   #2
MAS1

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Quote:
 Originally Posted by LeroyTsruya Hi all! i have a problem solving this: given the function g: R->R g(x) = (2x^2 - x)/(3x^2 +x + 1) I have to determine g is an injective function, and also find its image. any ideas? Thanks!
The function g is injective if for all a and b in A, if g(a) = g(b), then a = b; that is, g(a) = g(b) implies a = b. Equivalently, if a ≠ b, then g(a) ≠ g(b).

Therefore, since g(0) = (2(0)^2 - 0)/(3(0)^2 + 0 + 1) = (0)/(1) = 0 and
g(1/2) = (2(1/2)^2 - (1/2))/(3(1/2)^2 + (1/2) + 1) = (0)/(2 1/4) = 0

then the function g(x) is not injective.

I'm not sure what you mean by image. Could you define it ?

 03-16-2010 #3 jmw106462 Last Achievements     Join Date: Feb 2010 Posts: 388 What Mas1 said. __________________ Please refrain from sending me frivolous PM's

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