f'(0), if f(x)=(2x-3)/(1+x²);
f'(x)=2(1+x²)-2x(2x-3)/(1+x²)²=2+2x²-4x²+6x/1+2x²+x⁴=-2x²+6x+2/x⁴+2x²+1;
f'(0)=2.
f'(0), if f(x)=(2x-3)/(1+x²);
f'(x)=2(1+x²)-2x(2x-3)/(1+x²)²=2+2x²-4x²+6x/1+2x²+x⁴=-2x²+6x+2/x⁴+2x²+1;
f'(0)=2.