Cho đa thức: P = 3 x^2 y - {xyz -(2xyz -x^2 z) - 4x^2 z + [2x^2 y

a) P=3x2y−xyz−(2xyz−x2z)−4x2z+3x2y−(4xyz−5x2z−3xyz)

=3x2y−xyz−2xyz+x2z−4x2z+3x2y−4xyz+5x2z+3xyz

=3x2y−xyz+2xyz−x2z+4x2z−3x2y+4xyz−5x2z−3xyz

=−2x2z+2xyz

b) P =−2.−12.3+2.−1.2.3 =−18