5.不等式组$\left\{\begin{array}{l}{x<a+1}\\{x>2}\end{array}\right.$有3个整数解,则a的取值范围是( )
| A. | 5<a≤6 | B. | 4<a≤5 | C. | 4≤a<5 | D. | 5≤a<6 |
4.下列计算中,正确的是 ( )
| A. | $\sqrt{5}-\sqrt{3}=\sqrt{2}$ | B. | $2+\sqrt{3}=2\sqrt{3}$ | C. | $\sqrt{8}×\sqrt{2}=4$ | D. | $\frac{{\sqrt{10}}}{2}=\sqrt{5}$ |
1.-27的立方根是( )
| A. | 3 | B. | 3或-3 | C. | -3 | D. | -9 |
20.
如图,一艘轮船在A处测得北偏东45°方向有一灯塔B,船向正东方向航行到达C处时,又观测到灯塔B在北偏东30°方向上,此时轮船与灯塔相距60海里,求轮船从A处到C处航行了多少海里(结果保留根号).
0 285927 285935 285941 285945 285951 285953 285957 285963 285965 285971 285977 285981 285983 285987 285993 285995 286001 286005 286007 286011 286013 286017 286019 286021 286022 286023 286025 286026 286027 286029 286031 286035 286037 286041 286043 286047 286053 286055 286061 286065 286067 286071 286077 286083 286085 286091 286095 286097 286103 286107 286113 286121 366461