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Factorise: 9x² − 25y²:

A(3x − 5y)(3x + 5y)
B(3x − 5y)²
C(9x − 25y)(x + y)
D(3x + 5y)²
Answer & Solution
Correct answer: A. (3x − 5y)(3x + 5y)
9x² = (3x)², 25y² = (5y)². **So 9x² − 25y² = (3x)² − (5y)² = (3x − 5y)(3x + 5y) by the difference-of-squares identity.**
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