A) 10
B) \[-\,10\]
C) 20
D) \[-\,20\]
Correct Answer: B
Solution :
\[{{(a+b+c)}^{2}}={{a}^{2}}+{{b}^{2}}+{{c}^{2}}+2\,(ab+bc+ca)\] \[\Rightarrow \] \[0=20+2(ab+bc+ca)\] \[\Rightarrow \] \[ab+bc+ca=\frac{-\,20}{2}=-10\]You need to login to perform this action.
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