Completing the square for  f(x) = x^2- 4x +2
 x^2- 4x + 2 = x^2- 4x  + (     ) - (     )  + 2

 where (     ) is half of the coefficient of x term squared
 x^2- 4x + 2 = x^2- 4x  + (-4/2)^2- (-4/2)^2+ 2
   		= { x^2- 4x  + (-2)^2} - (-2)^2+ 2
                  = { (x -2)^2} - 4  + 2
                  = (x -2)^2 - 2

Completing the square for f(x) = -2x^2+7x+1

-2x^2 +7x + 1 = -2(x^2 - 7/2x - 1/2)

-2(x^2 - 7/2x + 1/2) = -2(x^2 - 7/2x + (  ) - (  ) - 1/2)

where (  ) is half of the coefficient of x term squared
-2(x^2 - 7/2x + 1/2) = -2(x^2 - 7/2x + (-7/4)^2 - (-7/4)^2 - 1/2)
		     = -2({x^2 - 7/2x + 49/16} - 49/16 - 1/2)
                     = -2({x - 7/2}^2 - 57/16)
		     = 57/8 - 2(x - 7/2)^2