13.已知二次函数y=-$\frac{1}{2}$x2-3x-$\frac{5}{2}$,设自变量的值分别为x1、x2、x3,且-3<x1<x2<x3<3,则对应的函数值的大小关系是y1<y2<y3.
8.已知抛物线y=ax2+bx+c与x轴交于(x1,0)、(x2,0)两点,且0<x1<1,1<x2<5与y轴交于(0,-2),下列结论:①2a+b>1;②a+b<2;③3a+b>0;④a<-1,其中正确结论的个数为( )
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |
5.一元二次方程x2-8x=1配方后可变形为( )
0 290977 290985 290991 290995 291001 291003 291007 291013 291015 291021 291027 291031 291033 291037 291043 291045 291051 291055 291057 291061 291063 291067 291069 291071 291072 291073 291075 291076 291077 291079 291081 291085 291087 291091 291093 291097 291103 291105 291111 291115 291117 291121 291127 291133 291135 291141 291145 291147 291153 291157 291163 291171 366461
| A. | (x-4)2=15 | B. | (x+4)2=15 | C. | (x-4)2=17 | D. | (x+1)2=17 |