• 设,则3a3+12a2-6a-12= = .试题及答案-填空题-云返教育

    • 试题详情

      ,则3a3+12a2-6a-12=
      =

      试题解答


      【答案】根据已知条件表示出a+1=,然后把算式配成a-1的形式,再代入进行计算即可求解;
      先把分母提取公因式,然后再分母有理化整理即可得解.



      ∵a=-1,
      ∴a+1=
      3a3+12a2-6a-12
      =(3a3+6a2+3a)+(6a2+12a+6)-21a-18
      =3a(a+1)2+6(a+1)2-18
      =7×3a+6×7-21a-18
      =42-18
      =24;


      =+++…+
      =+++…+
      =1-+-+-+…+-
      =1-
      =
      故答案为:24,

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