b: \(8x^3\left(y+z\right)-y^3\left(z+2x\right)-z^3\left(2x-y\right)\)
\(=8x^3y+8x^3z-y^3z-2xy^3-z^3\left(2x-y\right)\)
\(=2xy\left(4x^2-y^2\right)+z\left(8x^3-y^3\right)-z^3\left(2x-y\right)\)
=2xy(2x-y)(2x+y)+z(2x-y)\(\left(4x^2+2xy+y^2\right)-z^3\left(2x-y\right)\)
=(2x-y)[2xy(2x+y)+z\(\left(4x^2+2xy+y^2\right)\) -z^3]


