Question

Perform the indicated operation. (3a2 - 7xy)(3a2 + 7xy)

Answer 1

(3a² - 7xy)(3a² + 7xy) =

= (3a²)² - (7xy)²

= 9a⁴ - 49x²y²

Use

a² - b² = (a - b)(a + b)

Answer 2

9a^4 - 49x^2y^2.

Explanation:

(3a^2 - 7xy)(3a^2 + 7xy)

This is example of the difference of 2 squares:

(a + b)(a - b) = a^2 - b^2, so the answer is:

(3a^2)^2 - (7xy)^2

= 9a^4 - 49x^2y^2.