Bonsoir,
(x+7) ( x+1 -1)
=(x+7)( x)
(2x-5) ( 2x-5 -x-2)
= (2x-5) ( x -7)
(2x+1) ( 1 + 5x -3x)
= (2x+1) ( 1 +2x)
(x-8) (x-8 +1)
= (x-8) ( x-7)
