You want to put this in the form (x+b)^2 + c
To do this take half of the coefficient of b from the ordinal form which is 6/2=3 as use this as your new b
This give you (x+3)^2.
If you foil this out you get x^2 +6x +9 so you have added 9 to the original expression so now all you need to do is subtract 9 to keep things balanced
The final expression then is (x+3)^2 -9
So c= -9
