题目内容

1
5
+
1
45
+
1
117
+
1
221
方法一:
1
5
+
1
45
+
1
117
+
1
221

=
1
5
+
1
5
×
1
9
+
1
9
×
1
13
+
1
13
×
1
17

=
1
5
×(1+
1
9
)+
1
13
×(
1
9
+
1
17
),
=
2
9
+
2
9
×
1
17

=
2
9
×(1+
1
17
),
=
2
9
×
18
17

=
4
17

方法二:
1
5
+
1
45
+
1
117
+
1
221

=4×(
1
5
+
1
45
+
1
117
+
1
221
)÷4,
=(
4
5
+
4
45
+
4
117
+
4
221
)÷4,
=(1-
1
5
+
1
5
-
1
9
+
1
9
-
1
13
+
1
13
-
1
17
)÷4,
=(1-
1
17
)÷4,
=
16
17
÷4,
=
4
17
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