bonjour
f (x) = ( 3 x + 1 )² - 49
1 ) f (x) = 9 x² + 6 x + 1 - 49 = 9 x² + 6 x - 48
2 ) f (x) = ( 3 x + 1 - 7 ) ( 3 x + 1 + 7 ) = ( 3 x - 6 ) ( 3 x + 8 )
3 ) f ( 0) = 9 * 0 + 6 * 0 - 48 = - 48
f ( 1/3 ) = 9 ( 1/3)² + 6 *1/3 - 48 = 9 * 1/9 + 6/3- 48 = 1 + 2 - 48 = - 45
f ( √5) = ( 3 √5 - 6 ) ( 3 √5 + 8 ) = 45 + 24 √5 - 18 √5 - 48 = - 3 + 6 √5
f (x) = 0
( 3 x - 6 ) ( 3 x + 8 ) = 0
x = 6/3 = 2 ou - 8/3
f (x) = - 48
9 x² + 6 x - 48 = - 48
9 x² + 6 x = - 48 + 48
9 x² + 6 x = 0
3 x ( 3 x + 2 ) = 0
x = 0 ou - 2/3
