Réponse :
f(x) = 1/2 (x+5/2) (5-x) = (-x/2+5/2) (x+5/2) = -x²/2 - 5x/4 + 5x/2 + (5/2)²
-x²/2 + 5x/4 +25/4 = -0,5 x² + 1,25 x + 6,25