Question

 Chứng minh: (x2 - xy - y).(x + y) + xy(y + 1) = x3 - y2

Answer 1

\(\left(x^2-xy-y\right)\left(x+y\right)+xy\left(y+1\right)\)

\(=x^3+x^2y-x^2y-xy^2-xy-y^2+xy^2+xy\)

\(=x^3-y^2\)

Answer 2

Ta có : \(VT = ( x^{2} - xy -y ) . (x +y) + xy (y + 1) \)

= \(x^{3} + x^{2}y - x^{2}y = xy^{2} -xy - y^{2} + xy^{2} + xy\)

= \(x^{3} - y^{2} = VP\)