$f(f(x)) = 1 + x^2$, then what is f(1)?

by Ziqin He   Last Updated August 14, 2019 06:20 AM

I get $f(f(a)) = a^2 + 1 = f(f(-a))$, and so $f(a)^2 + 1 = f(a^2 + 1) = f(-a)^2 + 1$, so $f(a) = f(-a)$ or $f(a) = -f(-a)$, but then I donot know what to do next. Thanks for any help.



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