n°49
f(x)=(x-4)²-1=(x-4-1)(x-4+1)=(x-3)(x-5)
f(x)=(x-3)(x-5)=x²-8x+15
f(rac(2))=17-8rac(2)
f(5)=0
f(0)=15
f(x)=0 donne x=3 ou x=5
n°50
f(x)=(3x+1)²-49=(3x+1-7)(3x+1+7)=(3x-6)(3x+8)
f(x)=9x²+6x-48
f(0)=-48
f(1/3)=2²-49=-45
f(rac(2))=-30+6rac(2)
f(x)=0 donne x=2 ou x=-8/3
f(x)=--48 donne x=0 ou x=-2/3
