(21)12(1)
1 5 12 21 27 ( )
圆的轴对称性(1) (12 21:50:22)
6,12,12,18,21,( )
21(1)(2)
0,1,2,4,8,9,10,12,15,21,21,27,91质数( )合数()奇数( )偶数( )
(9 12)(12 16)(14 21)(24 32)(15 35)(28 49) (19 16)(15 3)(20 1
(1×2×3+2×4×6+4×8×12+7×14×21)÷(1×3×5+2×6×10+4×12×20+7×21×35)
5 12 21 34 53 80 ()
3 4 5 12 21 )
1,1,6,21,81,( ),( )
找规律填空.(1)9,12,21,33,(),().(2)1,4,9,16,25,(),()64,81
-3(1-6分之x) -12(3X-21)整式去括号