(8d³+8d²+3d±1)-(d³+6d²)=?
$$(8d^3+8d^2+3d\pm1)-1(d^3+6d^2)\\ =8d^3+8d^2+3d\pm1-d^3-6d^2\\ =8d^3-d^3+8d^2-6d^2+3d\pm1\\ =7d^3+2d^2+3d\pm1\\$$