3.已知函数$f(x)=\frac{1}{3}{x^3}-{x^2}+ax-5$在[-1,2]上不单调,则实数a的取值范围是( )
| A. | [-3,1) | B. | (-3,0) | C. | (-3,1) | D. | (-3,1] |
2.将4名学生分别安排甲、乙、丙三个地方参加实践活动,每个地方至少安排一名学生,则不同的安排方案共有( )
| A. | 12 | B. | 18 | C. | 24 | D. | 36 |
1.已知函数$f(x)=\left\{\begin{array}{l}-2x-{x^2},x≤0\\|{lgx}|,x>0\end{array}\right.$,若a<b<c<d,且f(a)=f(b)=f(c)=f(d),则a+b+c+2d的取值范围是( )
| A. | $({3,\frac{201}{10}})$ | B. | $({1,\frac{181}{10}})$ | C. | $({2\sqrt{2},+∞})$ | D. | $({2\sqrt{2}-2,+∞})$ |
20.已知$sinα+cosα=-\frac{{\sqrt{5}}}{2}$,且$\frac{5π}{4}<α<\frac{3π}{2}$,则cosα-sinα的值为( )
| A. | $-\frac{{\sqrt{3}}}{2}$ | B. | $\frac{{\sqrt{3}}}{2}$ | C. | $-\frac{3}{4}$ | D. | $\frac{3}{4}$ |
18.函数$y=\frac{2}{x}+ln\frac{1}{x-1}$的零点所在的大致区间是( )
0 239583 239591 239597 239601 239607 239609 239613 239619 239621 239627 239633 239637 239639 239643 239649 239651 239657 239661 239663 239667 239669 239673 239675 239677 239678 239679 239681 239682 239683 239685 239687 239691 239693 239697 239699 239703 239709 239711 239717 239721 239723 239727 239733 239739 239741 239747 239751 239753 239759 239763 239769 239777 266669
| A. | (0,1) | B. | (1,2) | C. | (2,3) | D. | (3,4) |