\[\boxed{\mathbf{596.}ОК\ ГДЗ\ –\ домашка\ на\ 5}\]
\[\textbf{а)}\ По\ правилу\ \]
\[параллелепипеда:\]
\[\overrightarrow{BD_{1}} = \overrightarrow{\text{BA}} + \overrightarrow{\text{BC}} + \overrightarrow{BB_{1}}.\]
\[\textbf{б)}\ По\ правилу\ треугольника:\]
\[\overrightarrow{B_{1}D_{1}} = \overrightarrow{B_{1}A_{1}} + \overrightarrow{A_{1}D_{1}}.\]
\[B_{1}B \parallel A_{1}A;\ \ \ B_{1}B = A_{1}A:\]
\[\overrightarrow{B_{1}A_{1}} + \overrightarrow{A_{1}B} = \overrightarrow{B_{1}B} = \overrightarrow{A_{1}A}\text{.\ }\]
\[Отсюда:\ \]
\[\overrightarrow{B_{1}A_{1}} = \overrightarrow{A_{1}A} - \overrightarrow{A_{1}B};\]
\[\overrightarrow{B_{1}D_{1}} = \overrightarrow{A_{1}A} - \overrightarrow{A_{1}B} + \overrightarrow{A_{1}D_{1}}.\]