(1)231×6.2+23.1×208﹣131×27;
(2)7
﹣1.125+(2.25﹣6
);
(3)1﹣2+3﹣4+5﹣6+7﹣8+9+97﹣98+99;
(4)1+
+
+
+…+
.
4+8+16=16×2﹣4=28
4+8+16+32=32×2﹣4=60
4+8+16+32+64=64×2﹣4=124
4+8+16+32+…+256=
a+2a+4a+8a+16a+…+1024a=
(1+0.12+0.23)×(0.12+0.23+0.34)﹣(1+0.12+0.23+0.34)×(0.12+0.23)=
66.6×7.6+334×0.24+13.36×38=
998877+988776+887766+877665+776655+766554+665544+655443=
(1×2×3×4×…×9×10×11)÷(28×27×25×24×22)=
1.23452+0.76552+2.469×0.7655=
C . 
D .
看算式,发现规律,找出答案.
3×6=18 33×66=2178 333×666=221778 3333×6666=22217778 …
=( )
B .
C .
D . 以上全错
①996+599-402
②7443+2485+567+245
③2000-1347-253+1593
④3675-(11+13+15+17+19)