If f(x) is an even function, which statement about the graph of f(x) must be true?

An even function satisfies f(−x) = f(x) for every x in its domain. This means the points (x, f(x)) and (−x, f(x)) both lie on the graph, so reflecting the graph across the y-axis leaves it unchanged. Therefore, the graph has line symmetry about the y-axis.

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