y=1/(x^2+1) 二阶求导,书上答案为(6x^2-2)/(x^2+1)^3,
问题描述:
y=1/(x^2+1) 二阶求导,书上答案为(6x^2-2)/(x^2+1)^3,
答
y=(x^2+1)^(-1)
y'=-2x(x^2+1)^(-2)
y''=-2(x^2+1)^(-2)+(-2)*2x*(x^2+1)^(-3)
=(6x^2-2)/(x^2+1)^3