5.若实数x,y满足不等式组$\left\{\begin{array}{l}{y-x≥0}\\{x+y-7≤0}\\{x≥0}\end{array}\right.$,则z=2x+y的最大值是( )
| A. | $\frac{7}{2}$ | B. | $\frac{21}{2}$ | C. | 14 | D. | 21 |
4.等差数列{an}满足a1=39,a1+a3=74,则通项公式an=( )
| A. | -2n+41 | B. | -2n+39 | C. | -n2+40n | D. | -n2-40n |
3.已知圆的方程是x2+y2=1,则经过圆上一点M(1,0)的切线方程是( )
| A. | x=1 | B. | y=1 | C. | x+y=1 | D. | x-y=1 |
2.集合A={-2,-1,0,1,2},B={-1,2,3},则A∪B=( )
| A. | {-2,-1,0,1,2} | B. | {-1,2,3} | C. | {-2,-1,0,1,2,3} | D. | {-1,2} |
1.已知f(x)=sin(ωx+θ),其中ω>0,θ∈(0,$\frac{π}{2}$),f(x1)=f(x2)=0,|x2-x1|min=$\frac{π}{2}$.f(x)=f($\frac{π}{3}-x$),将f(x)的图象向左平移$\frac{π}{6}$个单位得G(x),则G(x)的单调递减区间是( )
| A. | [kπ,kπ+$\frac{π}{2}$] | B. | [kπ+$\frac{π}{6}$,kπ+$\frac{2π}{3}$] | C. | [kπ+$\frac{π}{3}$,kπ+$\frac{5π}{6}$] | D. | [kπ+$\frac{π}{12}$,kπ+$\frac{7π}{12}$] |
20.在棱长为2的正方体ABCD-A1B1C1D1中,M是棱A1D1的中点,过C1,B,M作正方体的截面,则这个截面的面积为( )
0 238381 238389 238395 238399 238405 238407 238411 238417 238419 238425 238431 238435 238437 238441 238447 238449 238455 238459 238461 238465 238467 238471 238473 238475 238476 238477 238479 238480 238481 238483 238485 238489 238491 238495 238497 238501 238507 238509 238515 238519 238521 238525 238531 238537 238539 238545 238549 238551 238557 238561 238567 238575 266669
| A. | $\frac{3\sqrt{5}}{2}$ | B. | $\frac{3\sqrt{5}}{8}$ | C. | $\frac{9}{2}$ | D. | $\frac{9}{8}$ |