Bonsoir,
On a : f(x) = (-5x+1)(x+7)
La forme développée :
(-5x+1)(x+7) = -5x²-35x+x+7 = -5x²-34x+7
a = -5, b = -34 , c = 7
La forme canonique: a(x-α)²+β
α = -b/2a = -34/10 = -17/5
β = f(α) = -5×(-17/5)²-34×(-17/5)+7 = -5×(289/25)-578/5 + 7 = -289/5 + 578/5 + 35/5 = 324/5
Forme canonique => -5(x+17/5)²+324/5
