-2(x-1)x-(x+7)(x^2-7x+49)=-2x^2+2x-x^3+14x^2-49x-7x^2+49x^2-343=2x^3+54x^2-49x-343
-2(x-1)x-(x+7)(x^2-7x+49)=-(2*x^2-2x)-(x+7)*(x^2-7x+49)=-2x^2+2x-(x+7)*(x^2-7x+49)=-2x^2+2x-(x^3+343)=-x^3-2x^2+2x-343
-2(x-1)x-(x+7)(x^2-7x+49)=-2x^2+2x-x^3+14x^2-49x-7x^2+49x^2-343=2x^3+54x^2-49x-343
-2(x-1)x-(x+7)(x^2-7x+49)=-(2*x^2-2x)-(x+7)*(x^2-7x+49)=-2x^2+2x-(x+7)*(x^2-7x+49)=-2x^2+2x-(x^3+343)=-x^3-2x^2+2x-343