Thursday, May 2, 2013

The function f is defined as f(x)=(2x+1)/(x-3). Find the value of k so that the inverse of f is f^-1(x)=(3x+1)/(x-k).

We'll determine the inverse function
f^-1(x).


Let f(x)=y, such
as:


y = (2x+1)/(x-3)


We'll
multiply both sides by (x-3):


xy - 3y =
2x+1


We'll move 3y to the
right:


xy = 2x + 3y +1


We'll
subtract 2x both sides:


xy - 2x = 3y +
1


We'll factorize by x to the
left:


x(y - 2) = 3y + 1


We'll
divide by (y-2):


x =
(3y+1)/(y-2)


The inverse function is: f^-1(x) =
(3x+1)/(x-2)


Comparing with the given
expression of f^-1(x) = (3x+1)/(x-k), we'll identify k =
2.

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