Bonjour,
[tex]x^2+4x+4=26\\\\x^2+2\times x\times2+2^2=26\\\\(x+2)^2=26\Rightarrow a^2+2ab+b^2=(a+b)^2\\\\x+2=\pm\sqrt{26}\\\\x+2=\sqrt{26}\quad ou\quad x+2=-\sqrt{26}\\\\x=\sqrt{26}-2\quad ou\quad x=-\sqrt{26}-2\\\\\boxed{S=\left\{-\sqrt{26}-2\;;\;\sqrt{26}-2\right\}}[/tex]
