For which numbers a, b, c, and d will the function
f(x) = (ax + b) / (cx + d)
satisfy f(f(x)) = x for all x (for which this equation makes sense)?
The Attempt at a Solution
I'm not sure what to do, which is my problem. So far I think that I can plug in (ax + b) / (cx + d) for x, because that is when it will satisfy f(f(x)) = x, right?
So then I have:
So I'm not sure where I want to end up, or where to go from here :( Can someone help me? This is due tomorrow. All help is appreciated.
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