When deriving the quadratic formula by completing the square, what expression can be added to both sides of the equation to create a perfect square trinomial? c/2
c^2/4
b/a
b^2/4a^2

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.