Below is a "complete the square problem" from a math help site on the internet.

This is the original problem. 4x2 – 2x – 5 = 0
Move the loose number over to the other side. 4x2 – 2x = 5
Divide through by whatever is multiplied on the squared term.
x^2-1/2x=5/4. How did -2x suddenly become -1/2? Thanks!!

The instructions want you to "divide (both sides of the equation) by the coefficient of the squared term", which is 4.

-2x divided by 4 is = -x/2