(p-2)(p+3)-(p+1)(p-6)=
=p^2+3p-2p-6-(p^2-6p+p-6)=
=p^2+3p-2p-6-p^2+6p-p-6=6p
=p2+3p-2p-6-(p2-6p+p-6)=p2+3p-2p-6-p2+6p-p+6=6p
(p-2)(p+3)-(p+1)(p-6)=
=p^2+3p-2p-6-(p^2-6p+p-6)=
=p^2+3p-2p-6-p^2+6p-p-6=6p
=p2+3p-2p-6-(p2-6p+p-6)=p2+3p-2p-6-p2+6p-p+6=6p