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若关于x的一元二次方程x2+2x-k=0有两个不相等的实数根,则k的取值范围是 ...
若关于x的一元二次方程x2+2x-k=0有两个不相等的实数根,则k的取值范围是 .
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如图,二次函数y=ax
2+bx+c的图象开口向上,图象经过点(-1,2)和(1,0)且与y轴交于负半轴.结论:①abc<0;②2a+b>0;③a+c=1;(4)a>1.其中正确的结论的序号是( )
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B.②③④
C.②③
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如图,梯形ABCD中,AB∥DC,AB⊥BC,AB=2cm,CD=4cm.以BC上一点O为圆心的圆经过A、D两点,且∠AOD=90°,则圆心O到弦AD的距离是( )
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B.
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C.
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D.
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如图,小正方形的边长均为1,则下列图中的三角形(阴影部分)与△ABC相似的是( )
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A.
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D.
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A.
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D.
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