Mathematics for IGCSE & O level - Algebraic Manipulation (Section 2 - No. 41)

What is the factored form of 9x² - 30xy + 25y²?

(3x + 5y)²

(3x - 5y)²

(9x - 5y)(x - 5y)

(9x + 5y)(x + 5y)

The expression factors to (3x - 5y)(3x - 5y) or (3x - 5y)².