A) 12
B) 15
C) 18
D) 21
Correct Answer: D
Solution :
\[E=|\overrightarrow{a}-2\overrightarrow{b}{{|}^{2}}+|\overrightarrow{b}-2\overrightarrow{c}{{|}^{2}}+|\overrightarrow{c}-2\overrightarrow{a}{{|}^{2}}\] \[E=5\left( {{\overrightarrow{a}}^{2}}+{{\overrightarrow{b}}^{2}}+{{\overrightarrow{c}}^{2}} \right)-4\left( \overrightarrow{a}\cdot \overrightarrow{b}+\overrightarrow{b}\cdot \overrightarrow{c}+\overrightarrow{c}\cdot \overrightarrow{a} \right)\] \[E=15-4\left( \overrightarrow{a}\cdot \overrightarrow{b}+\overrightarrow{b}\cdot \overrightarrow{c}+\overrightarrow{c}\cdot \overrightarrow{a} \right)\le 15-4\left( \frac{-3}{2} \right)\] \[E\le 21\]You need to login to perform this action.
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