0 55556 55564 55570 55574 55580 55582 55586 55592 55594 55600 55606 55610 55612 55616 55622 55624 55630 55634 55636 55640 55642 55646 55648 55650 55651 55652 55654 55655 55656 55658 55660 55664 55666 55670 55672 55676 55682 55684 55690 55694 55696 55700 55706 55712 55714 55720 55724 55726 55732 55736 55742 55750 266669
+7C
+10C
+…+(3n+1)C
=(3n+2)·2n-1.
)n展开式中的倒数第三项的系数为45，求：
)log5x-1+1］n的展开式中各奇数项二项式系数之和为32，中间项为2 500，求x.