bonjour,
E (x) = ( 3 x - 1 )² - ( x - 4 ) ( 3 x - 1 )
E (x) = 9 x² - 6 x + 1 - ( 3 x² - x - 12 x + 4 )
E (x) = 9 x² - 6 x + 1 - 3 x² + 13 x - 4
E (x) = 6 x² + 7 x - 3
E (x) = ( 3 x - 1 ) ( 3 x - 1 - x + 4 )
E ( x) = ( 3 x - 1 ) ( 2 x + 3 )
f ( - 2/3) = 6 ( - 2/3)² + 7 ( - 2/3) - 3
f ( - 2/3) = 6 * 4/9 - 14/3 - 3
f ( - 2/3) = 24/9 - 42/9 - 27/9
f ( - 2/3 ) = - 45/9 = - 5
b ) 6 x² - 7 x - 3 = - 3
6 x² - 7 x - 3 + 3 = 0
6 x² - 7 x = 0
x ( 6 x - 7 ) = 0
donc x = 0 ou 7/6
