等价的因为y+根号(y^2-1)=[y+根号(y^2-1)][y-根号(y^2-1)]/[y-根号(y^2-1)]=[y^2-(y^2-1)]/[y-根号(y^2-1)]=1/[y-根号(y^2-1)]所以y+根号(y^2-1)=e^(x-1)->1/[y+根号(y^2-1)]=1/[e^(x-1)][y-根号(y^2-1)]=e^(-(x-1))
