How do you complete the square?
You start off with a formula in the form y = x2 + bx. The first step is to add the square of half of the coefficient of x: (b/2)2. This allows us to rearrange the formula into (x+ b/2)2 . However, our formula is not equal to what we started with since we added (b/2)2 so we have to subtract it from the end. If the formula you start with has a constant (a term without the variable x) you ignore it in order to rearrange the x2 +bx part and then add it back on at the end as it will combine with the (b/2)2 term we subtracted.
