\(VT=n\left(n+1\right)\left(n+2\right)\left(n+3\right)+2\)
\(VT=\left[n\left(n+3\right)\right]\left[\left(n+1\right)\left(n+2\right)\right]+2\)
\(VT=\left(n^2+3n\right)\left(n^2+2n+n+2\right)+2\)
\(VT=\left(n^2+3n\right)\left(n^2+3n+2\right)+2\)
\(Vt=\left(n^2+3n+1-1\right)\left(n^2+3n+1+1\right)+2\)
\(VT=\left(n^2+3n+1\right)^2-1+2\)
\(VT=\left(n^2+3n+1\right)^2+1=VP\left(đpcm\right)\)