Cho các đa thức: A = 5 x^3 y - 4xy^2 - 6 x^2 y^2; B = -8 xy^3 + xy^2

a) A−B−C=(5x3y−4xy2−6x2y2)−(−8xy3+xy2−4x2y2)−(x3+4x3y−6xy3−4xy2+5x2y2)

=5x3y−4xy2−6x2y2+8xy3−xy2+4x2y2−x3−4x3y+6xy3+4xy2−5x2y2

=x3y−xy2−7x2y2+14xy3−x3

b) B+A−C=(−8xy3+xy2−4x2y2)+(5x3y−4xy2−6x2y2)−(x3+4x3y−6xy3−4xy2+5x2y2)

=−8xy3+xy2−4x2y2+5x3y−4xy2−6x2y2−x3−4x3y+6xy3+4xy2−5x2y2

=−2xy3+xy2−15x2y2+x3y−x3

c) C−A−B=(x3+4x3y−6xy3−4xy2+5x2y2)−(5x3y−4xy2−6x2y2)−(−8xy3+xy2−4x2y2)

=x3+4x3y−6xy3−4xy2+5x2y2−5x3y+4xy2+6x2y2+8xy3−xy2+4x2y2

=x3−x3y+2xy3−xy2+15x2y2