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Determinantes por Sarrus

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Calcula aplicando la Regla de Sarrus el determinante de la siguiente matriz:

 A =
\left(
\begin{array}{ccc}
     1 & -1 & 1
  \\ 2 & 0 & 1
  \\ 1 & 2 & -1
\end{array}
\right)

SOLUCIÓN

Determinante 3×3 — Regla de Sarrus

\left|\begin{array}{ccc}1 & -1 & 1 \\ 2 & 0 & 1 \\ 1 & 2 & -1\end{array}\right|

Diagonales principales ↘ (productos positivos):

\left|\begin{array}{ccc}{\color[RGB]{0,0,0}{1}} & {\color[RGB]{30,100,220}{-1}} & {\color[RGB]{200,30,30}{1}} \\ {\color[RGB]{200,30,30}{2}} & {\color[RGB]{0,0,0}{0}} & {\color[RGB]{30,100,220}{1}} \\ {\color[RGB]{30,100,220}{1}} & {\color[RGB]{200,30,30}{2}} & {\color[RGB]{0,0,0}{-1}}\end{array}\right|

{\color[RGB]{0,0,0}{1}}{\cdot}{\color[RGB]{0,0,0}{0}}{\cdot}{\color[RGB]{0,0,0}{(-1)}}+{\color[RGB]{30,100,220}{(-1)}}{\cdot}{\color[RGB]{30,100,220}{1}}{\cdot}{\color[RGB]{30,100,220}{1}}+{\color[RGB]{200,30,30}{1}}{\cdot}{\color[RGB]{200,30,30}{2}}{\cdot}{\color[RGB]{200,30,30}{2}}={\color[RGB]{0,0,0}{0}}+{\color[RGB]{30,100,220}{(-1)}}+{\color[RGB]{200,30,30}{4}}=3

Diagonales secundarias ↗ (productos negativos):

\left|\begin{array}{ccc}{\color[RGB]{0,155,50}{1}} & {\color[RGB]{110,0,200}{-1}} & {\color[RGB]{0,0,0}{1}} \\ {\color[RGB]{110,0,200}{2}} & {\color[RGB]{0,0,0}{0}} & {\color[RGB]{0,155,50}{1}} \\ {\color[RGB]{0,0,0}{1}} & {\color[RGB]{0,155,50}{2}} & {\color[RGB]{110,0,200}{-1}}\end{array}\right|

{\color[RGB]{0,0,0}{1}}{\cdot}{\color[RGB]{0,0,0}{0}}{\cdot}{\color[RGB]{0,0,0}{1}}+{\color[RGB]{0,155,50}{1}}{\cdot}{\color[RGB]{0,155,50}{1}}{\cdot}{\color[RGB]{0,155,50}{2}}+{\color[RGB]{110,0,200}{(-1)}}{\cdot}{\color[RGB]{110,0,200}{2}}{\cdot}{\color[RGB]{110,0,200}{(-1)}}={\color[RGB]{0,0,0}{0}}+{\color[RGB]{0,155,50}{2}}+{\color[RGB]{110,0,200}{2}}=4

\det=3-4=\boxed{-1}

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