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Question

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Answer 1

f'(x)=((x-1)'(x²+1)-(x²+1)'(x-1))/(x²+1)²= (x(x²+1)-2x(x-1))/(x²+1)² =

=( x³+x-2x²+2x)/(x²+1)²= (x³-2x²+3x)/(x²+1)²

f'(1)= (1-2+3)/(1+1)²=2/2=1