(From the 1995 Russian Math Olympiad, Grade 9)
Let $f(x) = x^2 + 4x + 2$. Find all $x$ such that $f(f(x)) = 2$. russian math olympiad problems and solutions pdf verified
(From the 2007 Russian Math Olympiad, Grade 8) (From the 1995 Russian Math Olympiad, Grade 9)