Question

Which of the following is the product of (3x − 5) and (3x + 5)?

A. 9x2 − 25
B. 9x2 − 30x − 25
C. 9x − 10
D. 9x2 + 25

Answer 1

Explanation:

These binomials make up the difference of squares.

3x * 3x = 9x^2

3x * 5 = 15x

-5 * 3x = - 15x

-5 * 5 = - 25

Notice the 2nd and 3rd terms. They are equal except that one is plus and the other minus. That means they cancel. You are left with

9x^2 - 25