问题描述： x=f'(t) y=tf'(t)-f(t)的三阶导数?二阶已知为1/f"(t) 1个回答 分类：数学 2014-10-08 问题解答： 我来补答 x=f'(t)y=tf'(t)-f(t)dy/dx=[dy/dt]/[dx/dt]=[f'(t)+tf''(t)-f'(t)]/f''(t)=td^2y/dx^2=[d(dy/dx)/dt]/[dx/dt]=1/f''(t)d^3y/dx^3=[d(d^2y)/dt]/[dx/dt]=[d(1/f''(t))/dt]/f''(t)=[-f'''(t)/(f''(t))^2]/f''(t)=-f'''(t)/[f''(t)]^3 展开全文阅读
