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

Given x^2-5x+c=7, the constant term c will be obtained using the formula:
c=(-b/2a)²
given that a=1 and b=-5 then plugging the values we shall have:
c=(-(-5)/2*1)²
c=(5/2)²
c=25/4

Answer: the constant is 25/4