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给出下列命题:其中真命题为 (填上序号) ①∃α∈R,使得sin3α=3sinα...
给出下列命题:其中真命题为
(填上序号)
①∃α∈R,使得sin3α=3sinα; ②∀k∈R,曲线
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表示双曲线;
③∀a∈R
+,y=ae
xx
2的递减区间为(-2,0)④∃a∈R,对∀x∈R,使得x
2+2x+a<0.
考点分析:
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