Isn't it obvious?

Algebra Level 4

If f ( f ( x ) ) = f ( x ) f(f(x))=f(x) , then it follows that f ( x ) = x f(x)=x .

True For real x only If and only if x = 0 , 1 x={0,1} False

Manuel Kahayon by Manuel Kahayon , 21, Philippines

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1 solution

Manuel Kahayon
Mar 4, 2016

A good counterexample would be f ( x ) = ∣ x ∣ f(x) = |x|

1 Helpful 0 Interesting 0 Brilliant 0 Confused

Another counterexample is any constant function, f ( x ) = 3 f(x)=3 is what I used.

Spencer Whitehead - 5 years, 3 months ago

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