Hello, please consider the following.
[tex]x^2 + 10x + 25 = 8\\\\\text{\bf We can notice that } x^2+10x+25=(x+5)^2 \text{ so}\\\\x^2 + 10x + 25 = (x+5)^2=8\\\\\text{\bf We take the root.}\\\\x+5=\pm\sqrt{8}\\\\\text{\bf We subtract 5}\\\\\boxed{x=-5-\sqrt{8}} \ \ or \ \ x=-5+\sqrt{8}[/tex]
In the box, you can find the smallest solution.
Thank you.