1.1. Find the matrix $C=2 A+B$, if

$$
A=\left(\begin{array}{ll}
2 & 1 \\
3 & 4
\end{array}\right), B=\left(\begin{array}{cc}
0 & -5 \\
-1 & 6
\end{array}\right)
$$
S o l u t i o n. According to the definition of linear operations on matrices and their properties, we have:

$$
C=2\left(\begin{array}{ll}
2 & 1 \\
3 & 4
\end{array}\right)+3\left(\begin{array}{cc}
0 & -5 \\
-1 & 6
\end{array}\right)=\left(\begin{array}{cc}
4 & 2 \\
6 & 8
\end{array}\right)+\left(\begin{array}{cc}
0 & -15 \\
-3 & 18
\end{array}\right)=\left(\begin{array}{cc}
4 & -13 \\
3 & 26
\end{array}\right)
$$

Remark. The problem could also be solved as follows:

$$
C=\left(\begin{array}{cc}
2 \cdot 2+3 \cdot 0 & 2 \cdot 1+3 \cdot(-5) \\
2 \cdot 3+3 \cdot(-1) & 2 \cdot 4+3 \cdot 6
\end{array}\right)=\left(\begin{array}{cc}
4 & -13 \\
3 & 26
\end{array}\right)
$$