1. Use the Euclidean algorithm to find the greatest common divisor (GCD) of the following sets of numbers, and express it as an integer linear combination of these numbers: (i) $15, 21, -35$; (ii) $210, -330, 1155$.
(i) $(15,21)=3=3 \cdot 15-2 \cdot 21, (3,-35)=1=3 \cdot 12-35$. Therefore, $(15,21,-35)=1=12(3 \cdot 15-2 \cdot 21)-35=36 \cdot 15-24 \cdot 21+(-35)$;
(ii) $(210,-330)=30(7,-11)=30, 1=-3 \cdot 7-2 \cdot(-11), 30=-3 \cdot 210-$
$$\begin{aligned}
2 \cdot(-330) \cdot(30,1155)=15(2,77) & =15, 15=-38 \cdot 30+1155 . \text{ So } \\
(210,-330,1155) & =15=38(3 \cdot 210+2 \cdot(-330))+1155 \\
& =114 \cdot 210+76 \cdot(-330)+1155 .
\end{aligned}$$