12.{an}是各项均为正数的等差数列,{bn}是等比数列,已知$\frac{a_1}{b_1}$=$\frac{a_2}{b_2}$=1,$\frac{a_3}{b_3}$=$\frac{8}{9}$,那么$\frac{a_4}{b_4}$=( )
| A. | $\frac{20}{27}$ | B. | $\frac{16}{27}$ | C. | $\frac{4}{9}$ | D. | $\frac{20}{27}$或$\frac{16}{27}$ |
11.将一根绳子对折,然后用剪刀在对折过的绳子上任意一处剪断,则得到的三条绳子的长度可以作为三角形的三边形的概率为( )
| A. | $\frac{1}{6}$ | B. | $\frac{1}{4}$ | C. | $\frac{1}{3}$ | D. | $\frac{1}{2}$ |
10.等比数列{an}的第5项恰好等于前5项之和,那么该数列的公比q=( )
| A. | -1 | B. | 1 | C. | 1或-1 | D. | 2 |
5.已知函数f(x)=-x3-x+sinx,若关于x的不等式$f(\frac{1}{x})+f(x-m)>0$在$[\frac{1}{2},2]$上有解,则实数m的取值范围是( )
0 234653 234661 234667 234671 234677 234679 234683 234689 234691 234697 234703 234707 234709 234713 234719 234721 234727 234731 234733 234737 234739 234743 234745 234747 234748 234749 234751 234752 234753 234755 234757 234761 234763 234767 234769 234773 234779 234781 234787 234791 234793 234797 234803 234809 234811 234817 234821 234823 234829 234833 234839 234847 266669
| A. | $m<\frac{5}{2}$ | B. | $m>\frac{5}{2}$ | C. | m<2 | D. | m>2 |