题目内容
(1+
+
+…+
)×(
+
+…+
)-(1+
+
+…+
)×(
+
+…+
).
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设
+
+…
=a,则:
(1+
+
+…
)×(
+
+…+
)-(1+
+
+…+
)×(
+
+…
)
=(1+a)(a+
)-(1+a+
)×a,
=a+
+a2+
-a-a2-
,
=
.
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(1+
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=(1+a)(a+
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=a+
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| a |
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=
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