Bonsoir,
A=
x² -6x +9 -8 +6x
= x² +1
B=
2 identités remarquables
25x² +10x +1 -(4x² -2x +2x -1)
= 25x² +10x +1 -4x² +2x -2x +1
= 21x² +10x +2