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问题 填空题

二次函数y=x2+（2+k）x+2k与x轴交于A，B两点，其中点A是个定点，A，B分别在原点的两侧，且OA+OB=6，则直线y=kx+1与x轴的交点坐标为______．

答案

∵A，B分别在原点的两侧，A点在左侧，且OA+OB=6，

∴设A（a，0），则B（6+a，0），

∵函数y=x2+（2+k）x+2k的图象与x轴的交点就是方程x2+（2+k）x+2k=0的根，

∴a+6+a=-（2+k），a•（6+a）=2k，

即2a=-k-8，6a+a2=2k，

解得a=-8，或a=-2，

当a=-2时，k=-4，

∴直线y=kx+1为直线y=-4x+1，与x轴交点坐标为（

1
4
，0），

当a=-8时，k=8，

∴直线y=kx+1为直线y=8x+1，与x轴交点为（-

1
8
，0）（不合题意舍去）

故直线y=kx+1与x轴的交点坐标为（

1
4
，0）．

单项选择题

阅读下面短文，从短文后各题所给的四个选项（A、B、C 和 D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

                                    A Heroic Driver

Larry works with Transport Drivers. Inc. One morning in 2009. Larry was  41

along 165 north after delivering to one of his    42   . suddenly, he saw a car with its bright lights on.    43    he got closer, he found 44    vehicle upside down on the road. One more look and he noticed    45    shooting out from under the    46    vehicle. Larry pulled over, set the brake and    47   the fire extinguisher (灭火器). Two good bursts from the extinguisher and the fire was put out.

The man who had his bright lights on    48    and told Larry he had    49    an emergency call. They    50    heard a woman’s voice coming from the wrecked (毁坏的) vehicle.    51   the vehicle, they saw that a woman was trying to get out of the broken window. They told her to stay    52    until the emergency personnel arrived,    53    she thought the car was going to    54   . Larry told her that he had already put out the fire and she should not move    55    she injured her neck.

Once fire and emergency people arrive, Larry and the other man    56    and let them go to work. Then, Larry asked the    57    if he was needed or    58    to go. They let him and the other man go.

One thing is    59   —Larry went above and beyond the call of duty by getting so close to the burning vehicle! His    60    most likely saved the woman’s life.

54（）

A.explode

B.slip away

C.fall apart

D.crash
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单项选择题

高温炼焦时半焦变为焦炭的温度区间是（）

A.650～950

B.750～950

C.850～950
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