17.设等比数列{an}的前n项和为Sn=4(a1+a3+…+a2n-1),a1a2a3=27,则a6=( )
| A. | 27 | B. | 81 | C. | 243 | D. | 729 |
14.已知函数f(x)=|lgx|,若方程f(x)=k有两个不等的实根α,β,则$\frac{1}{α}+\frac{1}{β}$的取值范围是( )
| A. | (1,+∞) | B. | [1,+∞) | C. | (2,+∞) | D. | [2,+∞) |
13.已知f(x)=sinωx+cosωx(ω>0),若$y=f({x+θ})({0<θ<\frac{π}{2}})$是周期为π的偶函数,则θ的值是( )
| A. | $\frac{π}{8}$ | B. | $\frac{π}{6}$ | C. | $\frac{π}{4}$ | D. | $\frac{π}{3}$ |
12.设D为△ABC所在平面内的一点,且满足$\overrightarrow{BC}=2\overrightarrow{CD}$,则( )
0 233394 233402 233408 233412 233418 233420 233424 233430 233432 233438 233444 233448 233450 233454 233460 233462 233468 233472 233474 233478 233480 233484 233486 233488 233489 233490 233492 233493 233494 233496 233498 233502 233504 233508 233510 233514 233520 233522 233528 233532 233534 233538 233544 233550 233552 233558 233562 233564 233570 233574 233580 233588 266669
| A. | $\overrightarrow{AD}=\frac{1}{2}\overrightarrow{AB}+\frac{3}{2}\overrightarrow{AC}$ | B. | $\overrightarrow{AD}=-\frac{1}{2}\overrightarrow{AB}+\frac{3}{2}\overrightarrow{AC}$ | C. | $\overrightarrow{AD}=-\frac{3}{2}\overrightarrow{AB}+\frac{1}{2}\overrightarrow{AC}$ | D. | $\overrightarrow{AD}=\frac{3}{2}\overrightarrow{AB}-\frac{1}{2}\overrightarrow{AC}$ |