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质点在平面直角坐标系中的坐标为x=2m，y=3m,则该质点的位置矢量为m。

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两辆车A和B,在笔直的公路上同向行驶,它们从同一起始线上同时出发,并且由出发点开始计时,行驶的距离x(m)与行驶时间t(s)的函数关系式:A为xA=4t+t2,B为xB=2t2+2t3.（写在t后的数字是次幂,小数点后保留两位有效数字）(1)它们刚离开出发点时,行驶在前面的一辆车是;(2)出发后,两辆车行驶距离相同的时刻是;(3)出发后,B车相对A车速度为零的时刻是.

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一物体以恒定的速率v1向东运行，当它刚到达距离出发点为d的一点时，立即以恒定的速率v2往回运动并回到原处。问：（1）全程的平均速度是？（2）全程的平均速率是？

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Which of the following is not correct?

A. By saving a larger portion of its GDP, a country can raise its output per worker.
B. Savers supply their money to the financial system with the expectation that they will get it back with interest at a later date.
C. Financial intermediaries are the only type of financial institution.
D. The financial system helps match people’s saving with other people’s borrowing.

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Which of the following is correct?

A. Lenders sell bonds and borrowers buy them.
B. Long-term bonds usually pay a lower interest rate than do short-term bonds because long-term bonds are riskier.
Corporations sell bonds to raise funds.
D. None of the above is correct.

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