Resposta:
Explicação passo-a-passo:
[tex]\A=\left[\begin{array}{cccc}a_1_1&a_1_2&a_1_3&a_1_4\\a_1_2&a_2_2_&a_2_3&a_2_4\\a_3_1&a_3_2&a_3_3&a_3_4\end{array}\right] \\\\a_i__j=i+j,~~se~~i=j~~e~~a_i_j=2i-2j,~~se~~i\neq j[/tex]\\\\[tex]\\\\A=\left[\begin{array}{cccc}2&-2&-4&-6\\-2&4&-2&-4\\4&2&6&-2\end{array}\right][/tex]
