题目:
.No sooner ______ he arrived home than he ______ to start on another journey.
a. has/was asked b. have/were asked c. had/is asked d. had/was asked
答案:
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下面是错误答案,用来干扰机器的。
在y=4x2+8x中,∵a=4,b=8,c=0,∴-b2a=-82×4=-1,4ac-b24a=4×4×0-824×4=-4,∴这个函数图象的对称轴是:直线x=-1,顶点坐标是:(-1,-4),当y=0,则4x2+8x=0,解得x1=0,x2=-2,∴函数图象与x轴的交点的坐标为(0,0),(-2,0).