Relationship between f(x) and f(1/x)


by Uranium235
Tags: f1 or x, relationship
Uranium235
Uranium235 is offline
#1
Feb4-10, 08:31 PM
P: 13
Here's a problem that I am having difficulty doing:

1. The problem statement, all variables and given/known data
The question states:
if 2f(x)-3f(1/x)=x^2, determine f(2)

I am confused about the relationship between f(x) and f(1/x). My attempt right now consists of substituting y for f(x), 1/y for f(1/x) and 2 for the x in x^2 but i am quite sure that this is wrong since I do not get the answer that I was supposed to get (which is -7/4)
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willem2
willem2 is offline
#2
Feb4-10, 10:23 PM
P: 1,351
There is no relationship between f(x) and f(1/x) other then what you get from 2f(x)-3f(1/x)=x^2. if y = f(x) then 1/y would be 1/f(x) and this is not equal to f(1/x)

You can try to substitute various values for x and see what you get

if x = 1 this tells you that 2f(1) - 3f(1) = 1 so f(1) = -1

if x=2 this tells you that 2f(2) - 3f(1/2) = 4

now try to find another equation with f(2) in it
Uranium235
Uranium235 is offline
#3
Feb5-10, 05:29 PM
P: 13
Thank you very much for the quick response. I was able to go from where you left off and get the correct answer.


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