求所确定的隐函数y= y(x)的导数dy/dx
问题描述：
求所确定的隐函数y= y(x)的导数dy/dx
(x^2)y - lny = x
答
(x^2)y - lny = x
2x*y+x^2*y'-1/y*y'=1
(x^2-1/y)*y'=1-2xy
y'=(1-2xy)/(x^2-1/y)