Jeffrey's computer crashed again this morning. The manager _____ for a technician from the computer store to check and repair it.
A.
is arranged
B.
have arranged
C.
has arranged
D.
arranges
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参考答案:
举一反三
【简答题】已知数列b n 前n项和 S n = 3 2 n 2 - 1 2 n .数列a n 满足 3 a n = 4 -( b n +2) (n∈N * ),数列c n 满足c n =a n b n . (1)求数列a n 和数列b n 的通项公式; (2)求数列c n 的前n项和T n ; (3)若 c n ≤ 1 4 m 2 +m-1 对一切n恒成立,求实数m的取值范围.