1. Let $x \neq y$, and the sequences $x, a_{1}, a_{2}, a_{3}, y$ and $b_{1}, x, b_{2}, b_{3}$, $y, b_{4}$ are both arithmetic sequences, then $\frac{b_{4}-b_{3}}{a_{2}-a_{1}}=$ $\qquad$ .
1. Let the common differences of two sequences be $d, d^{\prime}$, then
$$
\begin{array}{rr}
y-x=4 d=3 d^{\prime}, \\
\therefore \quad \frac{d}{d^{\prime}}=\frac{3}{4}, \\
\frac{\left(b_{4}-b_{3}\right)}{\left(a_{2}-a_{1}\right)}=\frac{2 d^{\prime}}{d}=\frac{2 \times 4}{3}=2 \frac{2}{3} .
\end{array}
$$