(a+6)(a-1) (3-9m)(1+3m) (3n-4m)(2m-n) 7x(x--y)(7x+y) с ро чно

(a+6)(a-1)=a²-a+6a-6=a²++5a-6

(3-9m)(1+3m)=3(1-3m)(1+3m)
=3(1-9m²)

(3n-4m)(2m-n)=6mn-3n²-
-8m²+4mn=10mn-3n²-8m²

7x(x-2y)-(x-y)(7x+y)=
=7х²-14xy-(7х²+xy-7xy-y²)=
=7х²-14xy-7х²+6xy+y²=
=y²-8xy=y(y-8x)