f(x)=3(x-5)au carre +6 f(x)=-(z-1)au carre+3
f(x)=3(x-5)² appliquer (a-b)²=a²-2ab+b²
f(x)=3(x²-10x+25)=3x²-30x+75
f(x)=-(z-1)²+3=-(z²-2z+1)+3=-z²+2z-1+3=-z²+2z+2
