Đặt \(\left\{{}\begin{matrix}a=18x\\b=18y\end{matrix}\right.\) với \(x;y\in N\) và \(\left(x;y\right)=1\)
\(\Rightarrow18x+18y=162\)
\(\Rightarrow x+y=9\)
\(\Rightarrow\left(x;y\right)=\left(1;8\right);\left(2;7\right);\left(4;5\right)\)
\(\Rightarrow\left(a;b\right)=\left(18;144\right);\left(36;126\right);\left(72;90\right)\)