completing da square means lets say if u got A squared + 3A + 2 To complete the square you take the middle bit, 3A divide it by 2A which gives 3/2 then write (A+3/2) squared.If you multiply out the brackets you get A squared + 3A + 9/4. But we want A squared + 3A + 2 so you minus 1/4 and write A squared + 3A + 2 = (A+3/2) squared - (1/4).