14.等差数列{an}中,a2=1,公差d=2,则a3=( )
| A. | 1 | B. | 3 | C. | 5 | D. | 7 |
13.等比数列{an}中,a1=1,a4=8,则公比q等于( )
| A. | 1 | B. | 2 | C. | 3 | D. | 4 |
12.等差数列{an}中,a2+a8=10,则a5等于( )
| A. | 4 | B. | 5 | C. | 6 | D. | 7 |
9.在△ABC中,∠BAC=120°,AB=2,AC=1,P是BC边上的一点,则${(\overrightarrow{BP})^2}-\overrightarrow{AP}•\overrightarrow{BC}$的取值范围是( )
0 233647 233655 233661 233665 233671 233673 233677 233683 233685 233691 233697 233701 233703 233707 233713 233715 233721 233725 233727 233731 233733 233737 233739 233741 233742 233743 233745 233746 233747 233749 233751 233755 233757 233761 233763 233767 233773 233775 233781 233785 233787 233791 233797 233803 233805 233811 233815 233817 233823 233827 233833 233841 266669
| A. | $[\frac{1}{4},3]$ | B. | $[\frac{1}{2},5]$ | C. | $[\frac{13}{4},5]$ | D. | $[-\frac{27}{4},-5]$ |