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Explanation:
If g(x) is the inverse of f(x), and vice versa, then we have these two properties:
Since we want to find a function that is its own inverse, we want f(x) and g(x) to be the same function.
Through trial and error, you should find that f(x) = g(x) = x fit the description.
f(x) = x
f( g(x) ) = g(x) ... replace every x with g(x)
f( g(x) ) = x
You should find that g(f(x)) = x as well.
One possible answer is f(x) = x
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Through more trial and error, you should find that f(x) = g(x) = 1/x works as well. In fact, anything of the form f(x) = g(x) = k/x will work.
The proof can be written as follows
f(x) = k/x
f( g(x) ) = k/( g(x) )
f( g(x) ) = k/( k/x )
f( g(x) ) = (k/1) divide (k/x)
f( g(x) ) = (k/1) * (x/k)
f( g(x) ) = x
Through similar steps, you should find that g(f(x)) = x is the case also.
This proves that f(x) = k/x is its own inverse, where k is a real number constant.
Another possible answer is anything of the form f(x) = k/x
If we pick k = 3, then we get f(x) = 3/x which is the answer I wrote above.
You can pick any k value you want.
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There may be other types of functions that have this property, but I'm blanking on what they might be.
