3.若数列{an}满足:a1=2,an+1=$\frac{{a}_{n}-1}{{a}_{n}}$,则a7等于( )
| A. | 2 | B. | $\frac{1}{2}$ | C. | -1 | D. | 2018 |
2.满足A=60°,a=2$\sqrt{3}$,b=4的△ABC的个数是( )
| A. | 0 | B. | 1 | C. | 2 | D. | 3 |
20.已知函数f(x)=cos($\frac{2π}{3}$x)+(a-1)sin($\frac{π}{3}$x)+a,g(x)=3x-x,若f(g(x))≤0对任意的x∈[0,1]恒成立,则实数a的取值范围是( )
| A. | (-∞,$\sqrt{3}$-1] | B. | (-∞,0] | C. | [0,$\sqrt{3}$-1] | D. | (-∞,1-$\sqrt{3}$] |
19.已知抛物线x2=4y的焦点为F,设A(x1,y1),B(x2,y2)是抛物线上的两个动点,如满足y1+y2+2=$\frac{2\sqrt{3}}{3}$|AB|,则∠AFB的最大值( )
| A. | $\frac{π}{3}$ | B. | $\frac{2π}{3}$ | C. | $\frac{3π}{4}$ | D. | $\frac{5π}{6}$ |
17.若实数变量x、y满足约束条件|x+y|+|x-2y|≤3,目标函数z=ax-y+1(a∈R).有如下结论:①可行域外轮廓为矩形;②可行域面积为3;③a=1时,z的最小值为-1;④a=2时,使得z取最大值的最优解有无数组;则下列组合中全部正确的为( )
0 239357 239365 239371 239375 239381 239383 239387 239393 239395 239401 239407 239411 239413 239417 239423 239425 239431 239435 239437 239441 239443 239447 239449 239451 239452 239453 239455 239456 239457 239459 239461 239465 239467 239471 239473 239477 239483 239485 239491 239495 239497 239501 239507 239513 239515 239521 239525 239527 239533 239537 239543 239551 266669
| A. | ①② | B. | ②③ | C. | ①③ | D. | ③④ |