已知单调递增的等比数列{a
n}满足:a
2+a
3+a
4=28,且a
3+2是a
2和a
4的等差中项.
(Ⅰ)求数列a
n的通项公式{a
n};
(Ⅱ)令
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,S
n=b
1+b
2+…+b
n,求使S
n+n•2
n+1>50成立的最小的正整数n.
考点分析:
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