Respuesta :

3x^2−2x+7=0
3x^2−2x+1/3+7−1/3=0
3(x^2−2x/3+1/9)+7−1/3=0
3(x−1/3)^2+(21−1)/3=0
3(x−1/3)^2=−20/3
(x−1/3)^2=−20/9