x²-4x-3
a=1
b=-4
c=-3
delta=b²-4ac = 28
x1 = (-b+racine(delta))/2a
= (4+racine(28))/2 = 2+racine(28)
x2 = (-b-racine(delta))/2a
= (4-racine(28))/2 = 2-racine(28)
F(x) = a(x-x1)(x-x2)
F(x) = (x-2-racine(28)) (x-2+racine(28))
F(x) = (x-2-racine(4*7)) (x-2+racine(4*7))
F(x) = (x-2-racine(4)*racine(7)) (x-2+racine(4)*racine(7))
F(x) = (x-2-2*racine(7)) ((x-2+2*racine(7))
F(x) = (x-2(1+racine(7))) (x-2(1-racine(7)))
(x-2)²-7 = x²-4x+4-7 = x²-4x-3
