[tex]A= 5^{n}*4 ^{n+3}+ 5^{n+1}*4 ^{n+2}+5 ^{n+3} *4 ^{n}-5 ^{n+2} *4 ^{n+1}= \\ =5^{n}*4 ^{n}*(4 ^{3}+5 ^{1}*4 ^{2}+5 ^{3}-5 ^{2}*4 ^{1})= \\ = 5^{n}*4 ^{n}*(64+80+125-100)= \\ =5^{n}*4 ^{n}*169= \\ =5^{n}*4 ^{n}*13 ^{2} \\ A= 3^{n}*7 ^{n+2}- 3^{n+1}*7 ^{n+1}+3 ^{n+2} *7 ^{n+1}= \\ =3^{n}* 7^{n}*(7 ^{2} -3*7+3 ^{2}*7) = \\ =3^{n}* 7^{n}*91[/tex]