已知方程x2+2x-3=0和2x2+5x-3=0只有一个公共根，则以其他两根为根的方程是（）。
A.x2+3x+2=0
B.2x2-3x+1=0
C.3x2+2x+1=0
D.x2+2x+3=0
E.以上答案均不正确
参考答案：B
解析：
方程一化为(x-1)(x+3)=0，解得x1=1，x2=-3；方程二化为(2x-1)(x+3)=0，解得x2=-3，
．即求以
为解的方程．不妨将所求方程设为x2+bx+c=0，则有-b=x1+x3=
，即
| 完形填空。 | |||
| Traffic rules are made to keep order on the road. They also help to keep people __1__. The pedestrian (行人) has as many rules to __2__ as the driver of a car. You should walk at the sidewalk or at the __3__ of the road. Always look carefully before you walk across the street. If you like riding a bike, don't ride in the middle of the road or run __4__ red traffic lights. When you ride a bike with a friend, don't look around to talk. If you drive, you should __5__ at the traffic lights. You must always __6__ a seat belt (安全带). Without belts __7__ the driver and the passengers may be badly hurt in a sudden accident. Someone may be thrown out through the window. You may not need to drive a bus, but __8__ if you have to travel in one. Get on or get off a bus only when it has come to a __9__. When it is full, don't try to get inside _10__ you may fall off. Traffic rules are also called Road Safety rules. The maxim (格言)for all road users is "Thinking about others". | |||
| ( )1. A. healthy ( )2. A. follow ( )3. A. edge ( )4. A. through ( )5. A. speed up ( )6. A. take ( )7. A. half ( )8. A. look around ( )9. A. sign ( )10. A. and | B. safe B. make B. rim B. across B. go ahead B. wear B. neither B. take care B. stop B. so | C. happy C. break C. end C. along C. get off C. carry C. both C. take a seat C. corner C. or | D. careful D. pass D. side D. around D. slow down D. bring D. all D. look back D. crossing D. but |