Sửa đề: \(11^{n+2}+12^{2n+1}\)
Ta có: \(11^{n+2}+12^{2n+1}\)
\(=121\cdot11^n+12\cdot144^n\)
\(=\left(133-12\right)\cdot11^n+12\cdot144^n=133\cdot11^n+\left(144^n-11^n\right)\cdot12\)
Ta có: \(133\cdot11^n⋮133\forall n\)
\(\left(144^n-11^n\right)\cdot12⋮144-11⋮133\forall n\)
Do đó: \(133\cdot11^n+\left(144^n-11^n\right)\cdot12⋮13\forall n\)
hay \(11^{n+2}+12^{2n+1}⋮133\)