déterminer la forme canonique: f(x)= 3xcarré-12x+2

f(x)=3x²-12x+2
f(x)=3(x²-4x+2/3)
f(x)=3(x²-4x+4-4+2/3)
f(x)=3((x-2)²-12/3+2/3)
f(x)=3(x-2)²-10