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यदि a+b+c=0, |a|=6, |b|=8 |c|=10 है तो a.b+b.c+c.a का मान हैA. 100B. `-100`C. 200D. `-200` |
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Answer» Correct Answer - B हम जानते है `(a+b+c )^(2) =|a|^(2) +|b|^(2) +|c|^(2)` `" " +2 (a.b+b.c+c.a) ` दिया है ` |a| =6,|b| =8` `" " |c| =10` तथा `a+b+c=0` ` Arr " " 0=(6) ^(2) +(8)^(2) +(10)^(2) =2 " " (a.b+b.c+c.a)` ` rArr " " 2(a.b+b.c+c.a)=-200` ` therefore " " a.b+b.c+c.a=-100` |
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