Bonjour,
A (x) = - 2x² + 2x + 4
B (x) = (- 2x - 2) (x - 2)
B (x) = - 2x² + 4x - 2x + 4
B (x) = - 2x² + 2x + 4
C (x) = - 2 (x - 1/2)² + 9/2
C (x) = - 2 (x² - 2/2x + 1/4) + 9/2
C (x) = - 2x² + 4/2x - 2/4 + 9/2
C (x) = - 2x² + 2x - 1/2 + 9/2
C (x) = - 2x + 2x + 8/2
C (x) = - 2x + 2x + 4
Donc : A (x) = B (x) = C (x) .