ydx=(x-1)dy分离变量dy/y=dx/(x-1）lny=ln(x-1）+cy=（x-1）e^c当x=2时 y=1所以e^c=1 即c=0所以有y=x-1
分离变量得dx/(x-1)=dy/yln(x-1)=lny+Cx=2,y=1代入得C=0ln(x-1)=lny
