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(2006•武汉)(人教版)已知抛物线y=ax2+bx+c(a>0)的对称轴为直...
(2006•武汉)(人教版)已知抛物线y=ax
2+bx+c(a>0)的对称轴为直线x=-1,与x轴的一个交点为(x
1,0),且0<x
1<1,下列结论:①9a-3b+c>0;②b<a;③3a+c>0.其中正确结论的个数是( )
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A.0
B.1
C.2
D.3
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