Phá ngoặc rồi thu gọn.
Giải thích
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
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