a, A=x2y+13xy2+35xy2−2xy+3x2y−23A=x2y+13xy2+35xy2−2xy+3x2y−23

=x2y+xy23+35xy2−2xy+3x2y−23=x2y+xy23+35xy2−2xy+3x2y−23

=x2y+xy23+3xy25−2xy+3x2y−23=x2y+xy23+3xy25−2xy+3x2y−23

=4x2y+14xy215−2xy−23=4x2y+14xy215−2xy−23

b, Khi thay x = -1 và y = 1/2 thì đa thức trên đc

A=−12.12+13.(−1).(12)2+35(−1).(12)2−2(−1).(12)+3(−1)2.(12)−23A=−12.12+13.(−1).(12)2+35(−1).(12)2−2(−1).(12)+3(−1)2.(12)−23

=−12−112−320−2(−1).14+3.1.12−23=−12−112−320−2(−1).14+3.1.12−23

=−12−112−320+2.14+3.12−23=−12−112−320+2.14+3.12−23

=−12−112−320+12+32−23=−12−112−320+12+32−23

=35
dựa theo bài này là giải được