17.
已知,∠AOB=30°,点M1,M2,M3…在射线OB上,点N1,N2,N3…在射线0A上,△M1N1M2,△M2N2M3,△M3N3M4…均为等边三角形.若OM1=1,则△MnNnMn+1的边长为( )
| A. | 2n | B. | 2n+1 | C. | 2n-1 | D. | 2n |
16.若关于x的不等式组$\left\{\begin{array}{l}{x>3}\\{x<a}\end{array}\right.$无解,则a的取值范围是( )
| A. | a≤3 | B. | a≥3 | C. | a<3 | D. | a>3 |
15.已知a-b=1,则a2-b2-2b的值为( )
| A. | 1 | B. | 2 | C. | 3 | D. | 4 |
14.下列计算正确的是( )
0 306613 306621 306627 306631 306637 306639 306643 306649 306651 306657 306663 306667 306669 306673 306679 306681 306687 306691 306693 306697 306699 306703 306705 306707 306708 306709 306711 306712 306713 306715 306717 306721 306723 306727 306729 306733 306739 306741 306747 306751 306753 306757 306763 306769 306771 306777 306781 306783 306789 306793 306799 306807 366461
| A. | x2•x4=x8 | B. | (-a)2•a5=a7 | C. | 5×59=50 | D. | (-a)a5=-a5 |