4.以下列各组数为边长的三角形是直角三角形的是( )
| A. | 1,2,3 | B. | 5,6,7 | C. | 3,4,5 | D. | 6,7,8 |
18.下列各组线段能组成三角形的是( )
| A. | 1cm,2cm,4cm | B. | 8cm,6cm,4 cm | C. | 12cm,5cm,6cm | D. | 3cm,3cm,6cm |
17.下列计算正确的是( )
| A. | (a3)4=a7 | B. | a5÷a=a5 | C. | a3•a2=a6 | D. | (-2mn)3=-8m3n3 |
15.先化简,再求值:($\frac{{x}^{2}+x-4}{x-2}$-x-2)÷$\frac{x(x+2)}{{x}^{2}+4x+4}$,请你从-2,0,1,2中选择一个自己喜欢的数进行计算.
0 284749 284757 284763 284767 284773 284775 284779 284785 284787 284793 284799 284803 284805 284809 284815 284817 284823 284827 284829 284833 284835 284839 284841 284843 284844 284845 284847 284848 284849 284851 284853 284857 284859 284863 284865 284869 284875 284877 284883 284887 284889 284893 284899 284905 284907 284913 284917 284919 284925 284929 284935 284943 366461