Respuesta :
[tex]x^2+4x+1=0\\\\\underbrace{x^2+2x\cdot2+2^2}_{(x+2)^2}-2^2+1=0\\\\use\ (a+b)^2=a^2+2ab+b^2\\\\(x+2)^2-4+1=0\\\\(x+2)^2-3=0\\\\(x+2)^2=3\iff x+2=\sqrt3\ or\ x+2=-\sqrt3\\\\\boxed{x=\sqrt3-2\ or\ x=-2-\sqrt3}[/tex]