$a,M=\frac{2.8^{4}+27^{2}+4.6^{9}}{2^{7}.6^{7}+2^{7}+40.9^{4}}$
$=\frac{2.(2^{3})^{4}.(3^{3})^{2}+2^{2}.2^{9}.3^{9}}{2^{7}.2^{7}3^{7}+2^{7}.2^{3}.5(3^{2})^{4}}$
$=\frac{2.2^{12}.3^{6}+2^{112^{11}.3^{6}}.3^{9}}{2^{14}.3^{7}+2^{10}.5.3^{8}}$
$=\frac{2^{11}.3^{6}.(2^{2}+3^{3})}{2^{10}.3^{7}.(2^{4}+5.3)}$
$=\frac{2^{11}.3^{6}.31}{2^{10}.3^{7}.31}$
$=\frac{2}{3}$
Sai thì thui nha