Answer:
(y - 2)²
Step-by-step explanation:
9y² - 12y + 4 ← is a perfect square of the form
(ax - b)² = a²x² - 2abx + b²
Compare like terms with 9y² - 12y + 4, thus
a² = 9 ⇒ a = 3
b² = 4 ⇒ b = 2 and
- 2ab = - 2 × 3 × 2 = - 12
Thus
9y² - 12y + 4 = (3y - 2)²
