求微分方程y'x-y=3x
问题描述：
求微分方程y'x-y=3x
答
xy' - y = 3x
y' - y/x = 3,e^∫ - 1/x dx = e^- lnx = 1/x
1/x · y' - y/x² = 3/x
(y/x)' = 3/x
y/x = 3ln|x| + C
y = 3xln|x| + Cx