1.下列计算正确的是( )
| A. | (a4)3=a7 | B. | a8÷a4=a2 | C. | (ab)3=a3b3 | D. | (a+b)2=a2+b2 |
20.下列事件中,属于必然事件的是( )
| A. | 367人中至少有两人的生日相同 | |
| B. | 抛掷一次硬币正面朝上 | |
| C. | 任意买一张电影票,座位号是2的倍数 | |
| D. | 某种彩票的中奖率为1%,购买100张彩票一定中奖 |
17.
如图,AB是半圆O的直径,点C在半圆O上,把半圆沿弦AC折叠,$\widehat{AC}$恰好经过点O,则$\widehat{BC}$与$\widehat{AC}$的关系是( )
| A. | $\widehat{BC}$=$\frac{1}{2}$$\widehat{AC}$ | B. | $\widehat{BC}$=$\frac{1}{3}$$\widehat{AC}$ | C. | $\widehat{BC}$=$\widehat{AC}$ | D. | 不能确定 |
16.若关于x,y的二元一次方程组$\left\{\begin{array}{l}2x+y=3k-1\\ x+2y=-2\end{array}\right.$的解满足x+y=1,则k=( )
0 297420 297428 297434 297438 297444 297446 297450 297456 297458 297464 297470 297474 297476 297480 297486 297488 297494 297498 297500 297504 297506 297510 297512 297514 297515 297516 297518 297519 297520 297522 297524 297528 297530 297534 297536 297540 297546 297548 297554 297558 297560 297564 297570 297576 297578 297584 297588 297590 297596 297600 297606 297614 366461
| A. | -1 | B. | 1 | C. | 2 | D. | 3 |