(1)y=f(x)d^2y/dx^2=d(f'(x))/dx=f''(x)(2)y=ln[f(x)]dy/dx=f'(x)/f(x)d^2y/dx^2=d[f'(x)/f(x)]/dx=[f''(x)f(x)-f'(x)f'(x)]/f^2(x)=(f''(x)f(x)-[f'(x)]^2)/f^2(x)
