设函数y=y(x)由x=2t+|t|,y=5t^2+4t|t|,求dy

问题描述:

设函数y=y(x)由x=2t+|t|,y=5t^2+4t|t|,求dy

当t>=0时,x=2t+|t|=3t ,t=x/3则y=5t^2+4t^2=9t^2=x^2 ,则dy=2x dx ;
当t