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Suppose that f is a function such that 3f(x)-5xf(1/x)=x-7 for all non-zero real numbers x. Find f(2010)

 Apr 1, 2016

Best Answer 

 #1
avatar+6251 
+15

Suppose that f is a function such that 3f(x)-5xf(1/x)=x-7 for all non-zero real numbers x. Find f(2010)

\(3f(2010) - 5(2010)f\left(\dfrac 1 {2010}\right) = (2010)-7\)

\(3f(2010)-10050f\left(\dfrac 1 {2010}\right) = 2003\)

 

we can also write

\(3f\left(\dfrac 1 {2010}\right) - \dfrac {5}{2010}f(2010)=\dfrac 1{2010}-7=-\dfrac{14069}{2010}\)

 

\(let f(2010)=x, f\left(\dfrac 1 {2010}\right)=y\)

 

\(3x-10050y=2003\\ -\dfrac{5}{2010}x + 3y = -\dfrac{10469}{2010}\)

 

Solving this we get

\(x=2896\\\\ y = \dfrac{1337}{2010}\)

 

and thus

 

\(f(2010) = 2896\)

 Apr 2, 2016
edited by Rom  Apr 2, 2016
 #1
avatar+6251 
+15
Best Answer

Suppose that f is a function such that 3f(x)-5xf(1/x)=x-7 for all non-zero real numbers x. Find f(2010)

\(3f(2010) - 5(2010)f\left(\dfrac 1 {2010}\right) = (2010)-7\)

\(3f(2010)-10050f\left(\dfrac 1 {2010}\right) = 2003\)

 

we can also write

\(3f\left(\dfrac 1 {2010}\right) - \dfrac {5}{2010}f(2010)=\dfrac 1{2010}-7=-\dfrac{14069}{2010}\)

 

\(let f(2010)=x, f\left(\dfrac 1 {2010}\right)=y\)

 

\(3x-10050y=2003\\ -\dfrac{5}{2010}x + 3y = -\dfrac{10469}{2010}\)

 

Solving this we get

\(x=2896\\\\ y = \dfrac{1337}{2010}\)

 

and thus

 

\(f(2010) = 2896\)

Rom Apr 2, 2016
edited by Rom  Apr 2, 2016
 #2
avatar+129845 
0

I like the way you did this one, Rom....I have not seen this before.......very crafty !!!!

 

 

cool cool cool

 Apr 2, 2016

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