A) \[-2,-7\]
B) \[-2,7\]
C) \[2,-7\]
D) \[2,7\]
Correct Answer: C
Solution :
\[\left| \begin{matrix} x & 3 & 7 \\ 2 & x & -2 \\ 7 & 8 & x \\ \end{matrix} \right|\] \[\Rightarrow \]\[x({{x}^{2}}+16)-3(2x+14)+7(16-7x)=0\] \[{{x}^{3}}+16x-6x-42+112-49x=0\] \[\Rightarrow \]\[{{x}^{3}}-39x+70=0\] \[(x-5)({{x}^{2}}+5x-14)=0\Rightarrow x=5\] \[{{x}^{2}}+7x-2x-14=0\] \[\Rightarrow \]\[x(x+7)-2(x+7)=0\] \[x=2,-7\]
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