高阶导数：y=ln(1-x^2)
问题描述：
高阶导数：y=ln(1-x^2)
y=ln(1-x^2) 求y"
答
y'=(1-x^2)'/(1-x^2)=-2x/(1-x^2)
y''=-[(2x)'(1-x^2)-(2x)(1-x^2)'](1-x^2)
=-[2(1-x^2)-(2x)(-2x)]/(1-x^2)
=-(2+2x^2)/(1-x^2)
=2(x^2+1)/(x^2-1)