Question

Which of the following represents the factorization of the binomial below? 81x^2-25y^2

Answer 1

B. (9x - 5y) • (9x + 5y)

Multiply out to see why:

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

81x^2 + 45xy - 45xy - 25y^2

Middle 2 terms cancel to obtain

81x^2 - 25y^2

Answer 2

B. (9x - 5y)(9x + 5y)

Explanation:

Rewrite the binomial as:

(9x)² - (5y)²

Apply difference of two squares formula.

x² - y² = (x - y)(x + y)

(9x)² - (5y)² = (9x - 5y)(9x + 5y)