Dave Mattacks is a rock and folk drummer. He spent some years with the band Fairport Convention. He has also worked both as a session musician and as a performance artist.
... that will make it a perfect square trinomial of the form x2 + 2xy + y2. Since "2xy" in this case is (b/a)x, we must have y = b/(2a), so we add the square of b/(2a) to both ...