[tex]a\cdot b=(a,b)[a,b], deci \quad a\cdot b=12\cdot 144=1728,\\
\frac{a}{b}=\frac{3}{4},a= \frac{3b}{4}\\
a\cdot b=1728, \frac{3b^2}{4}=1728, b^2=\frac{1728\cdot 4}{3}\\b^2=2304,b=48\\
a= \frac{3\cdot 48}{4}=36, a+b=84[/tex]
(a,b)-cmmdc,[a,b]-cmmmc
