题目内容
1 |
5 |
1 |
45 |
1 |
117 |
1 |
221 |
方法一:
+
+
+
=
+
×
+
×
+
×
,
=
×(1+
)+
×(
+
),
=
+
×
,
=
×(1+
),
=
×
,
=
.
方法二:
+
+
+
,
=4×(
+
+
+
)÷4,
=(
+
+
+
)÷4,
=(1-
+
-
+
-
+
-
)÷4,
=(1-
)÷4,
=
÷4,
=
.
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 |
9 |
1 |
13 |
1 |
9 |
1 |
17 |
=
2 |
9 |
2 |
9 |
1 |
17 |
=
2 |
9 |
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 |
5 |
4 |
45 |
4 |
117 |
4 |
221 |
=(1-
1 |
5 |
1 |
5 |
1 |
9 |
1 |
9 |
1 |
13 |
1 |
13 |
1 |
17 |
=(1-
1 |
17 |
=
16 |
17 |
=
4 |
17 |
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