如图:在平行六面体 ABCD−A1B1C1D1 中， M 为 A1C1,B1D1 的交点.若 AB⇀=a⇀ ， AD⇀=b⇀ ， AA1⇀=c⇀ ，则向量 BM⇀=_刷题宝

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如图:在平行六面体 ABCD−A1B1C1D1 中， M 为 A1C1,B1D1 的交点.若 AB⇀=a⇀ ， AD⇀=b⇀ ， AA1⇀=c⇀ ，则向量 BM⇀= （）

A： $- \frac{1}{2} \overset{⇀}{a} + \frac{1}{2} \overset{⇀}{b} + \overset{⇀}{c}$

B： $\frac{1}{2} \overset{⇀}{a} + \frac{1}{2} \overset{⇀}{b} + \overset{⇀}{c}$

C： $- \frac{1}{2} \overset{⇀}{a} - \frac{1}{2} \overset{⇀}{b} + \overset{⇀}{c}$

D： $\frac{1}{2} \overset{⇀}{a} - \frac{1}{2} \overset{⇀}{b} + \overset{⇀}{c}$

上一题下一题 0.0难度选择题更新时间:2020-02-20 11:37:46

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A

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