简单分析一下，详情如图所示
dx = (arctant)'dt = 1/(1+t²) dtd(2y-ty+e^t) = 2dy -ydt-tdy+e^tdt =0有 (2-t)dy =(y-e^t)dt,即 dy = (y-e^t)/(2-t) dt所以dy/dx = (y-e^t)(1+t²) /(2-t)
