questions (in confusion)

9. Let \(f(x) = 2x + 7\) and \(g(x) = 3x + c\) . Find c if \(f(g(x)) = g(f(x))\) for all .

10. The function f(x) satisfies

\(f(\sqrt{x + 1}) = \frac{1}{x}\)
for all \(x \ge -1,\) \(x\neq 0.\) Find f(2).

11. Let \(f(x) = 3x^2 - 4x\). Find the constant k such that \(f(x) = f(k - x)\) for all real numbers x .