y=(2 x^3 + x^(1/2) + 4 ArcTan[x])/x
y'=(1/(2 Sqrt[x]) + 6 x^2 + 4/(1 + x^2))/x - ( Sqrt[x] + 2 x^3 + 4 ArcTan[x])/x^2
y''=(-(1/(4 x^(3/2))) + 12 x - (8 x)/(1 + x^2)^2)/x - ( 2 (1/(2 Sqrt[x]) + 6 x^2 + 4/(1 + x^2)))/x^2 + ( 2 (Sqrt[x] + 2 x^3 + 4 ArcTan[x]))/x^3sqrt什么意思根号