17.若x是有理数,则x2+1一定是( )
| A. | 等于1 | B. | 大于1 | C. | 不小于1 | D. | 不大于1 |
14.下列各数中,不一定有平方根的是( )
| A. | x2+1 | B. | |x|+2 | C. | $\sqrt{a}$+1 | D. | |a|-1 |
9.一块长方形草坪的长是3xa+1m,宽是2xb-1m(a,b为大于1的正整数),则长方形草坪的面积是( )
0 309842 309850 309856 309860 309866 309868 309872 309878 309880 309886 309892 309896 309898 309902 309908 309910 309916 309920 309922 309926 309928 309932 309934 309936 309937 309938 309940 309941 309942 309944 309946 309950 309952 309956 309958 309962 309968 309970 309976 309980 309982 309986 309992 309998 310000 310006 310010 310012 310018 310022 310028 310036 366461
| A. | 6xa-bm2 | B. | 6xa+bm2 | C. | 6xa+b-1m2 | D. | 6xa+b-2m2 |