简答题:用铁皮做一个容积为V的圆柱形有盖桶，证明当圆柱的高等于底面直径时，所使用的铁皮面积最小．

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114643_9461.png" width="14" height="25" /> B 2x C sinx D ln(x+e)

A e B e^-1 C e² D e^-2

A 0 B <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114655_7742.png" width="19" height="30" /> C 1 D 2

A -1 B 0 C 1 D 2

A -2 B 0 C 2 D 4

A 圆锥面 B 旋转抛物面 C 球面 D 椭球面

A -2 B -1 C 0 D 1

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114717_4305.png" width="86" height="27" />  B <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114721_0242.png" width="86" height="27" />  C <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114724_2899.png" width="86" height="27" />  D <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114728_0555.png" width="159" height="27" /> 

A (3，-1，2) B (1，-2，3) C (1，1，-1) D (1，-1，-1)

A 发散 B 条件收敛 C 绝对收敛 D 收敛性与a的取值有关