1.
Let lnx\ln x denote natural log. Let SRS\subset\mathbb R be all points where ln(x21)\ln(x^2-1) is well-defined. Number of differentiable functions f:SRf:S\to\mathbb R with f(x)=ln(x21)f'(x)=\ln(x^2-1) for xSx\in S and f(2)=0f(2)=0 is