b, \(\left(x+y\right)^3+\left(x-y\right)^3\)
\(=x^3+3x^2y+3xy^2+y^3+x^3-3x^2y+3xy^2-y^3\)
\(=2x^3+6xy^3=2x.\left(x^2+3y^3\right)\)
d, \(\left(x-y\right)^3-\left(x+y\right)^3\)
\(=x^3-3x^2y+3xy^2-y^3-\left(x^3+3x^2y+3xy^2+y^3\right)\)
\(=x^3-3x^2y+3xy^2-y^3-x^3-3x^2y-3xy^2-y^3\)
\(=-6x^2y-2y^3=-2y.\left(3x^2+y^2\right)\)
Chúc bạn học tốt!!!