f'=(x^2+3)^(-1/2)+x*(x^3+3)^(-3/2)*2x=(x^2+3)^(-1/2)(1+2x^2(x^2+3)^-1)
f'(1)=(1+3)^(-1/2)(1+2*1(1+3)^(-1))=3/4
f'=(x^2+3)^(-1/2)+x*(x^3+3)^(-3/2)*2x=(x^2+3)^(-1/2)(1+2x^2(x^2+3)^-1)
f'(1)=(1+3)^(-1/2)(1+2*1(1+3)^(-1))=3/4