【简答题】y'(t)+2y’(t)+2y(t)=f(t),y(0_)=0,y’(0_)=1,f(t)=u(t)
【单选题】They can’t dismiss you just like that. They have to give you a written _____ first.
【简答题】记∇为差分算子,则下列不正确的是( )。 A 12-∇-∇=∇t t t Y Y Y B2122--+-=∇t t t t Y Y Y Y C k t t t k Y Y Y --=∇ D t t t t Y X Y X ∇+∇=+∇)
【简答题】完成对话。 A: _______ me, Bill. Can you _______ me? I can't find _______ pencil. B: Isn't it _______ your bag? A: No, it _______. B: Please look _______ it under the desk. A: Oh, it is over there. Thank yo...