Ta có :
\(3^{n+3}+2^{n+3}+2^{n+2}+3^{n+1}\)
\(=\)\(3^n.3^3+2^n.2^3+2^n.2^2+3^n.3\)
\(=\)\(3^n\left(3^3+3\right)+2^n\left(2^3+2^2\right)\)
\(=\)\(3^n\left(27+3\right)+2^n\left(8+4\right)\)
\(=\)\(3^n.30+2^n.12\)
\(=\)\(3^n.5.6+2^n.2.6\)
\(=\)\(6\left(3^n.5+2^n.2\right)\)
Vì \(6⋮6\) nên \(6\left(3^n.5+2^n.2\right)⋮6\)
Vậy \(3^{n+3}+2^{n+3}+2^{n+2}+3^{n+1}⋮6\) với mọi số nguyên dương n
Chúc bạn học tốt ~