推 topee:感謝H大!! 04/08 17:51
※ 引述《topee (eason)》之銘言：
: Is the differential equation (2y+xy)dx + 2x dy = 0 exact?
: solve the differential equation
: 2ydx + xydx + 2xdy = 0
: 這題該用什麼方法解?
對2y+xy作y的偏微分,得2+x
對2x作x的偏微分,得2
兩個不相等 非正合
2ydx + xydx + 2xdy = 0
2d(xy) + xydx = 0
2ln(xy) + x = c
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