Question

factor.
$u^2 - 9$

Explanation:

Step1: Identify the form

The expression \( u^2 - 9 \) is a difference of squares, since \( u^2 \) is a square (\( (u)^2 \)) and \( 9 \) is a square (\( 3^2 \)). The formula for factoring a difference of squares is \( a^2 - b^2=(a + b)(a - b) \).

Step2: Apply the formula

Here, \( a = u \) and \( b = 3 \). Substituting into the formula, we get \( u^2 - 3^2=(u + 3)(u - 3) \).

Answer:

\((u + 3)(u - 3)\)