[tex]\displaystyle\bf\\F=m\cdot4^{3p+2}-3m\cdot4^{3p+1}+3n\cdot 4^{3p}=m\cdot 4^{3p}\cdot4^2 -3m\cdot 4^{3p}\cdot 4+3n\cdot 4^{3p}=\\4^{3p}(16m-12m+3n)=4^{3p}(4m+3n),~dar~4m+3n=15 \implies 15\cdot4^{3p}= 5\cdot3\cdot4^{3p}~\vdots~5,~evident.[/tex]
