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Question : 31 of 160
Marks:
+1,
-0
Solution:
From the given vectors,
b×c=|| =(4−25)−(−1−20)+(5+16) =−21+21+21 =21(−++) |b×c|=21√3 The vector r is perpendicular to b and c so,
r=±|r| Now,r.a=9‌so, ±[21(−++) .(3+−)]=9 ±[21(−3+1−1)]=9 |r|=3√3 This implies,
r=±3√3 =±3(−++) =−3(−++) or
3(−++)
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