1. Given that $x+y-2$ is a factor of the polynomial $x^{2}+a x y+b y^{2}-5 x+y+6$ in terms of $x, y$. Then the value of $a-b$ is $\qquad$ .
- 1.1.

When $x=0$, $y-2$ is a factor of $b y^{2}+y+6$, so $b=-2$.
When $x=y=1$,
$$
\begin{array}{l}
x^{2}+a x y+b y^{2}-5 x+y+6=0 \\
\Rightarrow 1+a+b-5+1+6=0 \\
\Rightarrow a=-1 .
\end{array}
$$

Therefore, $a-b=1$.