Phân tích thành nhân tử: xy(x + y) + yz(y + z) + xz(x + z) + 2xyz

xy(x + y) + yz(y + z) + xz(x + z) + 2xyz

= x2y + xy2 + yz(y + z) + x2z + xz2 + xyz + xyz

= (x2y + x2z) + yz(y + z) + (xy2 + xyz) + (xz2 + xyz)

= x2(y + z) + yz(y + z) + xy(y+ z) + xz(y + z)

= (y + z)( x2 + yz + xy + xz) = (y + z)[(x2 + xy) + (xz + yz)]

= (y + z)[x(x + y) + z(x + y)] = (y + z)(x+ y)(x + z)