老哥们，问个数学问题

BiskutHupSeng

2021-02-01T08:05:16+00:00

[img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-jgzvK11T3cSsg-g0.jpg.medium.jpg[/img]

这玩意儿怎么求？就是xixj双重求和的微分

Zireael

这玩意是个啥[s:ac:愁]

Danielm50

微积分都忘光了，大三那年考完就扔了
[img]http://img.nga.178.com/attachments/mon_201209/14/-47218_5052bc7a0ee49.png[/img]

BiskutHupSeng

[quote][pid=491051138,25425955,1]Reply[/pid] Post by [uid=2042231]wowpub[/uid] (2021-02-05 16:05):

这玩意是个啥[s:ac:愁][/quote]就是x1x1+x1x2+…x1xn+x2x1+x2x2+…+x2xn+…xnx1+xnx2+…xnxn[s:ac:哭笑]

SexyGamerChic

盲猜一手二重积分？

gladass

你就把d放进去再求和就完事儿了

Mr dripballs

直接微分号挪到最里面，求了微分再求和不就得了……

BiskutHupSeng

[quote][pid=491053281,25425955,1]Reply[/pid] Post by [uid=37634166]EEEEEEric[/uid] (2021-02-05 16:13):

你就把d放进去再求和就完事儿了[/quote][img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-5wctXeZ3tT3cSzk-qo.jpg.medium.jpg[/img]

是这样吗[s:ac:晕]

BiskutHupSeng

[quote][pid=491053405,25425955,1]Reply[/pid] Post by [uid=1612420]意识流_[/uid] (2021-02-05 16:13):

直接微分号挪到最里面，求了微分再求和不就得了……[/quote]是这样吗[s:ac:晕]

[img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-w5jXeZ3tT3cSzk-qo.jpg.medium.jpg[/img]

gladass

[quote][pid=491054386,25425955,1]Reply[/pid] Post by [uid=26464927]我爱杂粮饼[/uid] (2021-02-05 16:16):

是这样吗[s:ac:晕]

[img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-w5jXeZ3tT3cSzk-qo.jpg.medium.jpg[/img][/quote]少了一半，对j也要微分的

狼兄狗弟

早忘光了，告辞

kenziemarcoux

自信满满的点进来，一脸懵逼的走出去

Kairis

这就是我憎恨数学的原因，一低头一抬头就不知道跑哪儿去了，而且越往后数字越少

yitzmii

(dxi xj)+(xi dxj)括号外是求和符号

CrucialLaw

等等，你确定是这个式子？d里面不就是x1到xN求和的平方？

BiskutHupSeng

[quote][pid=491054699,25425955,1]Reply[/pid] Post by [uid=37634166]EEEEEEric[/uid] (2021-02-05 16:17):

少了一半，对j也要微分的[/quote][img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-53nuXbZ2zT3cSzk-qo.jpg.medium.jpg[/img]

那是这样吗[s:ac:呆]

BiskutHupSeng

[quote][pid=491056715,25425955,1]Reply[/pid] Post by [uid=60171190]mtchen92[/uid] (2021-02-05 16:23):

(dxi xj)+(xi dxj)括号外是求和符号[/quote][img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-ckuhXbZ2zT3cSzk-qo.jpg.medium.jpg[/img]

是这样吗[s:ac:呆]

SniperKills187

没记错的话是这样吧

[img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-autkKcT1kSgo-66.png[/img]

novajinkon923

感觉表述不对

BiskutHupSeng

[quote][pid=491059199,25425955,1]Reply[/pid] Post by [uid=34839766]BeerRabbit[/uid] (2021-02-05 16:30):

没记错的话是这样吧

[img]https://img.nga.178.com/attachments/mon_202102/05/-7Q16p-autkKcT1kSgo-66.png[/img][/quote]噢！感谢大佬！

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