bonjour
f (x) = ( x - 3 )² - 16
1. x² - 6 x + 9 - 16 = x² - 6 x - 7
2. ( x - 3 - 4 ) ( x - 3 + 4 ) = ( x - 7 ) ( x + 1 )
3. f ( 3) = 3² - 6 *3 - 7 = 9 - 18 - 7 = - 16
f ( - 3 ) = ( - 3 )² - 6 * - 3 - 7 = 9 + 18 - 7 = 20
f ( 3 + √2) = ( 3 + √2 - 7 ) ( 3 + √2 + 1 )
= 9 + 3 √2 + 3 + 3 √2 + 2 + √2 - 21 - 7√2 - 7
= -14
f (x) = 16
( x - 3 )² - 16 = - 16
( x - 3 )² - 16 + 16 = 0
( x - 3 )² = 0 donc x = 3
