a)
[tex]\left[\begin{array}{ccc}4\\-8\end{array}\right] .\left[\begin{array}{ccc}5&1\\\end{array}\right] = \left[\begin{array}{ccc}4.5&4.1\\(-8).5&(-8).1\end{array}\right]\\\\\\\left[\begin{array}{ccc}4.5&4.1\\(-8).5&(-8).1\end{array}\right] = \left[\begin{array}{ccc}20&4\\-40&-8\end{array}\right][/tex]
b)
[tex]\left[\begin{array}{ccc}-1&0&8\\4&5&2\\\end{array}\right] . \left[\begin{array}{ccc}6&9\\2&-3\\1&4\end{array}\right] = \left[\begin{array}{ccc}(-1.6 + 0.2+ 8.1)&(-1.9+0.(-3)+ 8.4)\\(4.6+5.2+2.1)&(4.9+5.(-3)+2.4)\\\end{array}\right]\\\\\\\left[\begin{array}{ccc}(-1.6 + 0.2+ 8.1)&(-1.9+0.(-3)+ 8.4)\\(4.6+5.2+2.1)&(4.9+5.(-3)+2.4)\\\end{array}\right]=\left[\begin{array}{ccc}2&23\\36&29\\\end{array}\right][/tex]
c) A matriz produto não está definida pois o número de colunas da matriz A₃ₓ₂ é diferente do número de linhas da matriz B₃ₓ₂ ( 2≠3) .
Espero ter ajudado!!!
