问题
选择题
It was half past seven, she ________. [ ]
A. is going to work
B. would go to work
C. were going to work
D. went to work
答案
答案:B
It was half past seven, she ________. [ ]
A. is going to work
B. would go to work
C. were going to work
D. went to work
答案:B
阅读理解下列例题: 例题:解一元二次不等式x2-2x-3<0. 分析:求解一元二次不等式时,应把它转化成一元一次不等式组求解. 把二次三项式x2-2x-3分解因式,得:x2-2x-3=(x-1)2-4=(x-3)(x+1),又x2-2x-3<0, ∴(x-3)(x+1)<0. 由“两实数相乘,同号得正,异号得负”,得
由①,得不等式组无解;由②,得-1<x<3. ∴(x-3)(x+1)<0的解集是-1<x<3. ∴原不等式的解集是-1<x<3. (1)仿照上面的解法解不等式x2+4x-12>0. (2)汽车在行驶中,由于惯性作用,刹车后还要继续向前滑行一段距离才能停住,我们称这段距离为“刹车距离”,刹车距离是分析事故的一个重要因素.某车行驶在一个限速为40千米/时的弯道上,突然发现异常,马上刹车,但是还是与前面的车发生了追尾,事故后现场测得此车的刹车距离略超过10米,我们知道此款车型的刹车距离S(米)与车速x(千米/时)满足函数关系:S=ax2+bx,且刹车距离S(米)与车速x(千米/时)的对应值表如下:
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