IME / ITA ⇒ (Escola Naval - 1978) Matrizes Tópico resolvido

[ALDRINMOD]

Se [tex3]A=\left[\begin{array}{cc} 2 & & 1 \\ 5 & & 3 \end{array}\right][/tex3] e [tex3]B=\left[\begin{array}{cc} 6 & & 4 \\ 8 & & 7 \end{array}\right][/tex3], então [tex3]AB[/tex3] é igual a:

(A) [tex3]\left[\begin{array}{cc} 20 & & 18 \\ 36 & & 45 \end{array}\right][/tex3].
(B) [tex3]\left[\begin{array}{cc} 20 & & 15 \\ 54 & & 41 \end{array}\right][/tex3].
(C) [tex3]\left[\begin{array}{cc} 15 & & 18 \\ 27 & & 35 \end{array}\right][/tex3].
(D) [tex3]\left[\begin{array}{cc} 15 & & 35 \\ 28 & & 40 \end{array}\right][/tex3].
(E) [tex3]\left[\begin{array}{cc} 18 & & 20 \\ 37 & & 40 \end{array}\right][/tex3].

[adrianotavares]

Olá, Aldrin.

[tex3]a_{11}= 2.6+1.8= 20[/tex3]

[tex3]a_{12}= 2.4+1.7= 15[/tex3]

[tex3]a_{21}= 5.6+3.8= 54[/tex3]

[tex3]a_{22}= 5.4+3.7= 41[/tex3]

Logo, a matriz [tex3]AB[/tex3] é igual a:

[tex3]\left[\begin{array}{cc} 20 & & 15 \\ 54 & & 41\end{array}\right][/tex3]

Alternativa : B