20.我国一次性建成最长的万吨重载铁路-晋豫鲁重载铁路,铁路全线长1260公里,横跨山西、河南、山东三省,总投资941亿元,941亿用科学记数法表示为( )
| A. | 941×108 | B. | 94.1×109 | C. | 9.41×1010 | D. | 9.41×1011 |
17.下列运算正确的是( )
0 284665 284673 284679 284683 284689 284691 284695 284701 284703 284709 284715 284719 284721 284725 284731 284733 284739 284743 284745 284749 284751 284755 284757 284759 284760 284761 284763 284764 284765 284767 284769 284773 284775 284779 284781 284785 284791 284793 284799 284803 284805 284809 284815 284821 284823 284829 284833 284835 284841 284845 284851 284859 366461
| A. | $\sqrt{16}$=±4 | B. | (3xy2)2=6x2y4 | C. | a3•a2=a5 | D. | ($\sqrt{2}+1$)($1-\sqrt{2}$)=1 |