Respuesta :

SvetkaChem

Answer:

4

Step-by-step explanation:

y² − 4y = 3

y² - 2*2*y =3

y² - 2*2*y  + 2² = 3 + 2²

(y - 2)² = 3 + 4
the constant that must be added is 4. that’s your answer.