f(x-1/x) = x⁴-4x²+1 / x²
f(x)=?
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f(1+√x / √x)=x²+x+1/x²
f(x)=?
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f: (-∞,1) -> (-∞,1) , f(x)=-x² + 2x
f^-1(x)=?
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