分析:(1)根据乘法分配律进行计算;
(2)根据乘法分配律进行计算;
(3)先算小括号里面的减法,再算中括号里面的加法,再按照从左向右的顺序进行计算;
(4)把带分数拆成整数与分数的和,然后再进一步计算即可;
(5)1234567890=1234567891-1,1234567892=1234567891+1,构成完全平方差公式,然后再进一步解答即可;
(6)根据分数的拆项进行计算即可.
解答:解:
(1)
÷-×,
=
,
=(
)×
,
=1×
,
=
;
(2)
[4-(3-2)×]÷,
=
[4-(-)×]÷,
=
[4-(×-×)]÷,
=
[-(-)]÷,
=
[-]÷,
=
×
,
=
;
(3)
12÷6×[2+(24.4-24)],
=
12÷6×[2+],
=
×
×
,
=
;
(4)
2+4+6+8+10+12,
=(2+4+6+8+10+12)+(
)
=(2+12)×6÷2+(
),
=42+(
-
+
-
+
-
+
-
+
-
),
=42+(
-
),
=42+
,
=42
;
(5)1234567891
2-1234567890×1234567892,
=1234567891
2-(1234567891-1)(1234567891+1),
=1234567891
2-(1234567891
2-1),
=1234567891
2-1234567891
2+1,
=1;
(6)
++++…+,
=
,
=
,
=
×(1-
),
=
×
,
=
.
点评:四则运算,先弄清运算顺序,然后再进一步计算,能简算的要简算.