\[\boxed{\mathbf{921.ОК\ ГДЗ - домашка\ на}\ 5}\]
\[\textbf{а)}\ x\overrightarrow{i} + y\overrightarrow{j} = 5\overrightarrow{i} - 2\overrightarrow{j}\]
\[x = 5\ и\ y = - 2.\]
\[\textbf{б)} - 3\overrightarrow{i} + y\overrightarrow{j} = x\overrightarrow{i} + 7\overrightarrow{j}\]
\[x = - 3\ и\ y = 7.\]
\[\textbf{в)}\ x\overrightarrow{i} + y\overrightarrow{j} = - 4\overrightarrow{i}\]
\[x = - 4\ и\ y = 0.\]
\[\textbf{г)}\ x\overrightarrow{i} + y\overrightarrow{j} = \overrightarrow{0}\]
\[x = 0\ и\ y = 0.\]