14.一个正多边形形的内角和是1440°,则它的每个外角的度数是( )
| A. | 30° | B. | 36° | C. | 45° | D. | 60° |
13.已知关于x、y的方程组$\left\{\begin{array}{l}{y-x=m-1}\\{2y+x=m+1}\end{array}\right.$的解x、y满足3x+y≥0,求m的取值范围.
6.下列命题中,假命题的是( )
0 284724 284732 284738 284742 284748 284750 284754 284760 284762 284768 284774 284778 284780 284784 284790 284792 284798 284802 284804 284808 284810 284814 284816 284818 284819 284820 284822 284823 284824 284826 284828 284832 284834 284838 284840 284844 284850 284852 284858 284862 284864 284868 284874 284880 284882 284888 284892 284894 284900 284904 284910 284918 366461
| A. | 两条直线平行,同位角相等 | B. | 对顶角相等 | ||
| C. | 同位角相等 | D. | 直角都相等 |