2x^2 + 4x + 1 =0 ==> x^2 + 2x + 1/2 = 0 ==> (x +1)^2 -1 + 1/2 = 0 ==> (x +1)^2 = 1/2 ==> |x +1| = √2 /2 ==> x = - 1 ±√2 /2