Let \[f(x) = \frac{2x + 3}{kx - 2}.\]Find all real numbers $k$ so that $f^{-1}(x) = f(x).$
I answered (-inf, inf) but its wrong.
interval notation
+118608 I'll start by stating that I do not have a clue.
Now the discussion:
when x=0 k can be anything
But, for any other given x, k cannot equal 2/x
But I don't know what the answer is. I tried graphing it but that just confused me more. 
Maybe it is \((-\infty, \frac{2}{x}) \cup (\frac{2}{x},\infty)\) where \(x\ne 0\) But I am guessing.
