bonjour
f (x) = ( 2 x - 6 ) ( - 12 x + 20 ) + 4 ( x - 3) ( 10 x - 12 )
f (x) = - 24 x² + 40 x + 72 x - 120 + 4 ( 10 x² - 12 x - 30 x + 36 )
= - 24 x² + 112 x - 120 + 40 x² - 48 x - 120 x + 144
= 16 x² - 56 x + 24
f (x) = 2 ( x - 3 ) ( - 12 x + 20) + 4 ( x - 3 ) ( 10 x - 12 )
= ( x - 3 ) ( - 24 x + 40 + 40 x - 48 )
= ( x - 3 ) ( 16 x - 8 )
= 4 ( x - 3 ) ( 4 x - 2 )
f (x) = ( 4 x - 7 )² - 25
= ( 4 x - 7 - 5 ) ( 4 x - 7 + 5)
= ( 4 x - 12 ) ( 4 x - 2 )
