2y'-y²-2yy't+e=0y'=(y²-e)/2(1-yt)t为函数方便，t=(5-2y)/(e-y²)2-t'y²-2yt+et'=0t'=2(1-yt)/(e-y²)=2[1-y(5-2y)/(e-y²)]/(e-y²)
