1. If $x, y \in R$, and $2^{x}=18^{y}=6^{x y}$, then $x+y$ $=$ . $\qquad$
Ni.1.0 or 2.
If $x=0$ or $y=0$, then it must be that $x=y=0$. Therefore, $x+y=0$.
If $x \neq 0$ and $y \neq 0$, taking the logarithm with base 6 of $2^{x}=18^{y}=6^{\circ}$, we get
$$
x \log _{6} 2=y \log _{6} 18=x y .
$$

Then $y=\log _{6} 2, x=\log _{6} 18$.
Thus, $x+y=\log _{6} 18+\log _{6} 2=\log _{6} 36=2$.
In conclusion, $x+y=0$ or 2.