12.
如图,已知顶点为(-3,-6)的抛物线y=ax2+bx+c经过点(-1,-4),则下列结论中错误的是( )
| A. | b2>4ac | |
| B. | ax2+bx+c≥-6 | |
| C. | 关于x的一元二次方程ax2+bx+c=-4的两根分别为-5和-1 | |
| D. | 若点(-2,m),(-5,n)在抛物线上,则m>n |
11.不等式组$\left\{\begin{array}{l}{x+1>2}\\{1-x≥-2}\end{array}\right.$的解集是( )
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| A. | x<1 | B. | x≥3 | C. | 1≤x<3 | D. | 1<x≤3 |