bonjour
1. vrai
2. ( 3 x + 7 )² - ( x- 1 )²
= 9 x² + 42 x + 49 - ( x² - 2 x + 1 )
= 9 x² + 42 x + 49 - x² + 2 x - 1
= 8 x² + 44 x + 48
3. faux
4. x² + 6 x + 9 / x² - 9 = x + 3 / x - 3
( x + 3 )² / ( x - 3 ) ( x + 3 ) = x + 3 / x - 3
( x + 3 ) ( x + 3 ) / ( x - 3 ) ( x + 3 ) = x + 3 / x - 3
= ( x + 3 ) / ( x - 3 )
