Resposta :
Larisa,
Veja as matrizes y a diagonal principal
a - A = 0 3
-3 1
Diagonal principal 0, 1 0 + 1 = 1
b -B = 1 0 3
4 2 -7
1 -6 5
Diagonal principal 1, 2, 5 1 + 2 + 5 = 8
c - C = 1/2 1/4
1/5 1/3 Diagonal principal 1/2, 1/3 1/2 + 1/3 = 5/6
a)
[tex]A = \begin{bmatrix} 0 & 3 \\ - 3 & 1 \end{bmatrix} \rightarrow 0 + 1 = \boxed{\boxed{1}}[/tex]
b)
[tex]B = \begin{bmatrix} 1 & 0 & 3 \\ 4 & 2 & - 7 \\ 1 & - 6 & 5 \end{bmatrix} \rightarrow 1 + 2 + 5 = \boxed{\boxed{8}}[/tex]
c)
[tex]C = \begin{bmatrix} \frac{1}{2} & \frac{1}{4} \\\\ \frac{1}{5} & \frac{1}{3} \end{bmatrix} \rightarrow \frac{1}{2_{/3}} + \frac{1}{3_{/2}} \rightarrow \frac{3 + 2}{6} = \boxed{\boxed{\frac{5}{6}}}[/tex]