Bonsoir,
A= ( 4x + 6 ) ( x + 5 ) + ( 4x² - 9) ₋ ( x + 1 )( 3 + 2x )
= 4x² +20x +6x +30 + 4x² -9 -( 3x +2x² +3 +2x)
= 4x² +20x +6x +30 + 4x² -9 - 3x -2x² -3 -2x
= 6x² +21x +21
B = x² + 16x + 64 + ( 5x ₋ 1)( x + 8) ₋ x² + 64
= x² +16x +64 +5x² +40x -x -8 -x² +64
= 5x² +55x +120