y=3(x² + 2x/3)=3[x² + 2x/3 + (1/3)² - (1/3)²]=3(x + 1/3)² - 3•(1/3)²=3(x + 1/3)² - 1/3
y=3x^2+2x =3*(x^2+2x/3) =3*(x+1/3)^2-1/3
