(y -3)^2 = 4y - 12
Expand.
(y-3)(y -3) = 4y - 12
y² - 6y + 9 = 4y - 12
y² - 6y -4y + 9 + 12 = 0
y² - 10y + 21 = 0
Factors are -7y and - 3y
y² - 10y + 21 = 0
y² - 3y - 7y + 21 = 0
y(y - 3) -7(y - 3) = 0
(y - 3)(y - 7) = 0
y-3 = 0 or y - 7 = 0
y = 0 + 3 or y = 0 + 7
y = 3 or 7
