【单选题】设L是从点A(-1,-1)沿曲线x 2 +xy+y 2 =3经点E(1,-2)到点B(1,1)曲线段,则曲线积分
【判断题】L是从点A(3,3)到点B(1,2) =4。
【单选题】When seeking to appoint new members to a corporation's board, the chairs traditionally looked for candidates who
A.
had legal and governmental experience.
B.
had experience dealing with community affairs.
C.
could work easily with other members of the board.
D.
were already involved in establishing policy for that corporation.
【判断题】L是从点A(3,2/3)到点B(1,2) =4。
【单选题】It can be inferred from the passage that, when seeking to appoint new members to a corporation's board, the chair traditionally looked for candidates who______.
A.
had experience dealing with community affairs
B.
could work easily with other members of the board
C.
were already involved in establishing policy for that corporation
D.
had influential connections outside the business world
【判断题】某发光二极管,两引脚一个长,一个短,则长引脚对应发光管的阴极。
【简答题】证明A=(2xy+3)i+(x 2 -4z)j-4yk为保守场,并计算曲线积分 其中l是从点A(3,-1,2)到点B(2,1,-1)的任意路径.