判斷下列命題真假,真命題個數(shù)有( )個
①用秦九少韶算法計算多項式
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在
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的值時,共進行了4次乘法和4次加法。
②在
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中,若
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則
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是等腰或直角三角形
③已知函數(shù)
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若
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則
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④若存在實數(shù)
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,使得
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,則
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。
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:方程
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有兩個不相等的負實數(shù)根;命題
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:函數(shù)

無零點.
(1)若
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的取值范圍;
(2)若
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或
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為真,

且

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
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
在R上遞增,Q:復(fù)數(shù)Z=(
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-4) +
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i所對應(yīng)的點在第二象限。如果P且Q為假,P或Q為真,求
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
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已知命題

:
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,

,命題
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:
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若命題“
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的取值范圍是_____________
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
:“
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”,命題

:“
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”
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
的取值范圍,使命題

為真命題
(Ⅱ)若“
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或
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”是真命題,“
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且
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
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有下列四個命題:
① “面積相等的三角形是全等三角形”的否定;② “若
xy = 0,則|
x | + |
y | = 0”的逆命題;③ “若
a>
b,則
a +
c>
b +
c”的否命題;④ “矩形的對角線互相垂直”的逆否命題.
其中真命題的個數(shù)是
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