Factor the perfect square trinomial \( x^2 - 30x + 225\).

\(\begin{align}
x^2 - 30x + 225 &=\left( {x + \frac{{\left( { -30} \right)}}{2}} \right)^2  \\
&=\left( {x - 15} \right)^2  \\
 \end{align}\)