What constant term should be used to complete the square? x 2 - 5x + = 7

The quadratic equation in its generic form is:
 ax2 + bx + c
 To complete squares we must add the following term:
 (b / 2) ^ 2
 The equation is:
 ax2 + bx + c + (b / 2) ^ 2
 We have the following equation:
 x ^ 2 - 5x + k = 7
 By completing squares we have:
 x ^ 2 - 5x + (-5/2) ^ 2 = 7 + (-5/2) ^ 2
 Rewriting:
 x ^ 2 - 5x + 6.25 = 7 + 6.25
 
 A constant term should be used to complete the square is:
 6.25