# Square root function?

Algebra Level 4

Consider a function $$f:\mathbb{N} \to \mathbb{R}$$, $$y=f(x)$$, which satisfies $$f(n) = \sqrt{f(n+1)}+c$$, where $$c \in \mathbb{R}$$ is a constant. If $$f(x)$$ is not a constant function and $$c \neq 0$$. Then which of the following about $$f(x)$$ can be true?

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