сгрупируем:
(7rn-14n)+(6r+12)=7n(r-2)+6(r+2)=(r-2)(7n-6)
может так...хз
7rn-6r-14n+12=(7rn-14n)+(-6r+12)=7n(r-2)-6(r-2)=(7n-6)(r-2)
сгрупируем:
(7rn-14n)+(6r+12)=7n(r-2)+6(r+2)=(r-2)(7n-6)
может так...хз
7rn-6r-14n+12=(7rn-14n)+(-6r+12)=7n(r-2)-6(r-2)=(7n-6)(r-2)