## College Algebra (10th Edition)

To complete the square of $x^2-4x$, add $4$.
To complete the square of $x^2-4x$, we must add half of the coefficient of x and square it. So, we would have: $(\frac{1}{2}\cdot-4)^2$ =$(-2)^2$ =$4$ To complete the square of $x^2-4x$, add $4$.