# Completing the square

The process of adding $(b/2)^2$, which is the square of half of the coefficient of $x$ in the expression $x^2 + bx$, to the expression. Consequently, $${x^2} + bx + {\left( {\frac{b}{2}} \right)^2} = {\left( {x + \frac{b}{2}} \right)^2}$$.