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用简便方法计算:(1+12+13+14)×(12+13+14+15)−(1+12+13+14+15)×(12+13+14)=.

题目详情
用简便方法计算:
(1+
1
2
+
1
3
+
1
4
)×(
1
2
+
1
3
+
1
4
+
1
5
)−(1+
1
2
+
1
3
+
1
4
+
1
5
)×(
1
2
+
1
3
+
1
4
)=______.
▼优质解答
答案和解析
1
2
+
1
3
+
1
4
=a,
1
2
+
1
3
+
1
4
+
1
6
=b,则:
(1+
1
2
+
1
3
+
1
4
)×(
1
2
+
1
3
+
1
4
+
1
5
)-(1+
1
2
+
1
3
+
1
4
+
1
5
)×(
1
2
+
1
3
+
1
4
),
=(1+a)×b-(1+b)×a,
=b+ab-a-ab,
=b-a,
=(
1
2
+
1
3
+
1
4
+
1
6
)-(
1
2
+
1
3
+
1
4
),
=
1
6

故答案为:
1
6