9.等差数列0,2,4,6,8,10,…按如下方法分组:(0),(2,4),(6,8,10),(12,14,16,18),…则第n组中n个数的和是( )
| A. | $\frac{n(2{n}^{2}-n-1)}{2}$ | B. | n(n2-1) | C. | n3-1 | D. | $\frac{n({n}^{2}-1)}{2}$ |
2.设偶函数f(x)满足f(x)=-x3+6(x≥0),则{x|f(x-2)>-2}=( )
| A. | (-2,4) | B. | (0,4) | C. | (0,6) | D. | (-2,2) |
1.曲线y=$\frac{1}{3}$x3+x在点(-1,-$\frac{4}{3}$)处的切线与坐标轴围成的三角形面积为( )
| A. | $\frac{1}{9}$ | B. | $\frac{2}{9}$ | C. | $\frac{1}{3}$ | D. | $\frac{2}{3}$ |
20.设函数f(x)=x2+bln(x+1),如果f(x)在定义域内既有极大值又有极小值,则实数b的取值范围是( )
0 230882 230890 230896 230900 230906 230908 230912 230918 230920 230926 230932 230936 230938 230942 230948 230950 230956 230960 230962 230966 230968 230972 230974 230976 230977 230978 230980 230981 230982 230984 230986 230990 230992 230996 230998 231002 231008 231010 231016 231020 231022 231026 231032 231038 231040 231046 231050 231052 231058 231062 231068 231076 266669
| A. | (-∞,$\frac{1}{2}$) | B. | (-∞,0)∪(0,$\frac{1}{2}$) | C. | (0,$\frac{1}{2}$) | D. | [0,$\frac{1}{2}$] |