判断向量组 $B$ 能否由向量组 $A$ 线性表示, 如果可以, 求出表达式.

(1) $A : \alpha_1=\left(\begin{array}{l}1 \\ 0 \\ 1\end{array}\right), \alpha _2=\left(\begin{array}{l}0 \\ 2 \\ 1\end{array}\right), \alpha_3=\left(\begin{array}{l}1 \\ 0 \\ 1\end{array}\right), B : \beta_1=\left(\begin{array}{l}1 \\ 2 \\ 1\end{array}\right), \beta_2=\left(\begin{array}{l}2 \\ 4 \\ 3\end{array}\right)$;

(2) $A : \alpha_1=\binom{1}{2}, \alpha_2=\binom{2}{1}, B : \beta_1=\binom{2}{3}, \beta_2=\binom{-1}{4}$;