题干
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=1﹣
，
=
﹣
，
=
﹣
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| 2 |
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| 2 |
| × |
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| × |
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将以上三个等式两边分别相加得：
+
+
=1﹣
+
﹣
+
﹣
=1﹣
=
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| × |
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| 2 |
| × |
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| 3 |
| × |
| 4 |
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下列关于该曲线的说法正确的是：（ ）
