Chapter 8 - Section 8.1 - The Square Root Property and Completing the Square - Concept and Vocabulary Check - Page 592: 6

$\frac{9}{4}$

$x^2 - 3x$ The coefficient of the x-term in $x^2 - 3x$ is $-3$. Half of $-3$ is $-\frac{3}{2}$, and $(-\frac{3}{2})^2 = \frac{9}{4}$ Add $\frac{9}{4}$. The result is a perfect square trinomial. $x^2 - 3x + \frac{9}{4} = (x -\frac{3}{2})^2$