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If $$f(x) = x^2 +5$$ for all positive integers $$x$$, which of the following must be true for each positive integer $$x$$?
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A.$$f(x)$$ is an odd integer.
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B.$$f(x)$$ is an even integer.
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C.$$f(x+1)$$ * $$f(x)$$is an odd integer.
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D.$$f(x+1)$$ + $$f(x)$$ is an even integer.
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E.$$f(x+1)$$ - $$f(x)$$ is an odd integer.
E显示答案
