Viết ma trận của dạng toàn phương Q trong cơ sở chính tắc: \(Q(\mathop x\nolimits_1 ,\mathop x\nolimits_2 ,\mathop x\nolimits_{3)} = 3\mathop {\mathop x\nolimits_1 }\nolimits^2 + \mathop {\mathop {2x}\nolimits_2 }\nolimits^2 - \mathop {\mathop x\nolimits_3 }\nolimits^2 + 2\mathop x\nolimits_1 \mathop x\nolimits_2 - 4\mathop x\nolimits_1 \mathop x\nolimits_3 + 2\mathop x\nolimits_2 \mathop x\nolimits_3\)
A. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 4}\\
2&2&2\\
{ - 4}&2&{ - 1}
\end{array}} \right)\)
B. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 4}\\
0&2&2\\
0&0&{ - 1}
\end{array}} \right)\)
C. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 2}\\
1&2&1\\
{ - 2}&1&{ - 1}
\end{array}} \right)\)
D. \(A = \left( {\begin{array}{*{20}{c}}
{ - 3}&2&{ - 4}\\
2&{ - 2}&2\\
{ - 4}&2&1
\end{array}} \right)\)
A. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 4}\\
2&2&2\\
{ - 4}&2&{ - 1}
\end{array}} \right)\)
B. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 4}\\
0&2&2\\
0&0&{ - 1}
\end{array}} \right)\)
C. \(A = \left( {\begin{array}{*{20}{c}}
3&2&{ - 2}\\
1&2&1\\
{ - 2}&1&{ - 1}
\end{array}} \right)\)
D. \(A = \left( {\begin{array}{*{20}{c}}
{ - 3}&2&{ - 4}\\
2&{ - 2}&2\\
{ - 4}&2&1
\end{array}} \right)\)