精英家教网 > 小学数学 > 题目详情
(1+
1
7
+
1
9
+
1
11
)
×(
1
7
+
1
9
+
1
11
+
1
21
)
-(1+
1
7
+
1
9
+
1
11
+
1
21
)
×(
1
7
+
1
9
+
1
11
)
分析:根据乘法分配律对原式进行变形解答.
解答:解:(1+
1
7
+
1
9
+
1
11
)
×(
1
7
+
1
9
+
1
11
+
1
21
)
-(1+
1
7
+
1
9
+
1
11
+
1
21
)
×(
1
7
+
1
9
+
1
11
)

=[1+(
1
7
+
1
9
+
1
11
)]×(
1
7
+
1
9
+
1
11
+
1
21
)
-[(1+(
1
7
+
1
9
+
1
11
+
1
21
)
(
1
7
+
1
9
+
1
11
)

=(
1
7
+
1
9
+
1
11
+
1
21
)
+(
1
7
+
1
9
+
1
11
)×(
1
7
+
1
9
+
1
11
+
1
21
)
-(
1
7
+
1
9
+
1
11
)
-(
1
7
+
1
9
+
1
11
+
1
21
)
×(
1
7
+
1
9
+
1
11
)

(
1
7
+
1
9
+
1
11
+
1
21
)
-(
1
7
+
1
9
+
1
11
)

=
1
21
点评:本题的关键是根据乘法分配律对题变形,再化简进行计算.
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