19.满足线性约束条件$\left\{\begin{array}{l}{2x+y≤3}\\{x+2y≤3}\\{x≥0,y≥0}\end{array}\right.$的目标函数x+3y的最大值是( )
| A. | $\frac{9}{2}$ | B. | $\frac{3}{2}$ | C. | 4 | D. | 3 |
17.点(a,a-1)在圆x2+y2-2y-9=0的内部,则a的取值范围是( )
| A. | -1<a<3 | B. | 1<a<3 | C. | $\frac{1}{5}$<a<1 | D. | -$\frac{1}{5}$<a<1 |
16.某几何体的三视图如图所示,则该几何体的体积为( )

| A. | $\frac{1}{3}$+π | B. | $\frac{2}{3}$+2π | C. | $\frac{8}{3}$+8π | D. | $\frac{4}{3}$+4π |
15.在等差数列{an}中,若a4+a9+a14=36,则2a10-a11=( )
| A. | 6 | B. | 12 | C. | 24 | D. | 36 |
13.已知点M(0,-2),点N在直线x-y-1=0上,若直线MN垂直于直线x+2y-3=0,则N点的坐标是( )
| A. | (-2,-3) | B. | (1,0) | C. | (2,3) | D. | (-1,0) |
12.已知α,β是平面,m,n是直线.下列命题中不正确的是( )
0 252290 252298 252304 252308 252314 252316 252320 252326 252328 252334 252340 252344 252346 252350 252356 252358 252364 252368 252370 252374 252376 252380 252382 252384 252385 252386 252388 252389 252390 252392 252394 252398 252400 252404 252406 252410 252416 252418 252424 252428 252430 252434 252440 252446 252448 252454 252458 252460 252466 252470 252476 252484 266669
| A. | 若m∥n,m⊥α,则n⊥α | B. | 若m∥α,α∩β=n,则m∥n | ||
| C. | 若m⊥α,m⊥β,则α∥β | D. | 若m⊥α,m∩β,则α⊥β |