※ 引述《tratt692 (jech)》之铭言：
: https://i.imgur.com/Awy8CSq.jpg
: 想问这题该怎么解
xy" - (x + 1)y' + y = 0
=> x[y' - y]' - [y' - y] = 0
=> y' - y = Cx
=> y = Aexp(x) - C(x + 1)