\(Tacó:\)
\(a=8a`;b=8b`\Rightarrow a+b=8\left(a`+b`\right)\Rightarrow a`+b`=6\)
\(\left(a< b\right)\Rightarrow a`< b`\left(a`,b`\ne0\right)\)
\(\Rightarrow b`\in\left\{4;5\right\}\)
\(+b`=4\Rightarrow b=32\Rightarrow a=16\Rightarrow UCLN\left(a,b\right)=16\left(loại\right)\)
\(+b`=5\Rightarrow b=40\Rightarrow a=8\Rightarrow UCLN\left(a,b\right)=8\left(thoảman\right)\)
Vậy: a=8;b=40