bonjour

(8x+3) (5x+7) -3 (8x+3)(2x-1)​

= ( 8 x + 3 ) ( 5 x + 7 - 6 x + 3 )

= ( 8 x + 3 ) ( - x + 10 )

Bsr

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

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

= (8x+3)(5x+7-6x+3)

= (8x+3)(-x+7+3)

= (8x+3)(-x+10)

Voilà !