1) 7х-7у+а(у-Х)=7(x-y)+a(y-x)=7(x-y)-a(x-y)=(7-a)(x-y)
2) 3с^2+15ас-2с-10а=(3c^2-2c)+(15ac-10a)=c(3c-2)+5a(3c-2)=(3c-2)(c+5a)
1) 7х-7у+а(у-Х)=7(x-y)+a(y-x)=7(x-y)-a(x-y)=(7-a)(x-y)
2) 3с^2+15ас-2с-10а=(3c^2-2c)+(15ac-10a)=c(3c-2)+5a(3c-2)=(3c-2)(c+5a)