What constant do you need to add to each quadratic to complete the square?

1    1/2  of -4 = -2    -2^2 = 4     Add 4

2    1/2 of -8 is -4    -4^2 =16    Add 16

3    Must have leading coefficient of 1 , so divide through by 3 to get

          x^2 + 6x = 8

          then  1/2 of 6 is 3     3^2 = 9    add 9

 

 

1/2 of  2/3  is   1/3    1/3^2 = 1/9      add 1/9