Verified answer

1) (х+7)(х²-7х+49)=х³+7³=х³+343

     -2(х-1)х=-2(х²-х)=-2х²+2х

      -2х²+2х-(х³+343)=-х³-2х²+2х-343

2) (b-6)(b²+6b+36)=b³-6³=b³-216

    2(b+1)(b+4)=2(b²+5b+4)=2b²+10b+8

 2b²+10b+8+b³-216=b³+2b²+10b-208

=-2х^2+2х-(x^3 - 7x^2 + 49x-7x^2+49x-343)=-2x^2 + 2x - x^3 + 7x^2 -49x + 7x^2 - 49x +343= -x^3 + 12x^2 -96x +343

=2(b^2 + 4b +b +4) + (b^3 - 6b^2 - 36 - 6b^2 +36b -216)= 2(b^2 + 5b + 4) + b^3 + 12b^2 -213 = 2b^2 + 10b + 8 + b^3 + 12b^2 -216 = b^3 +14b^2 +10b -208