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Algebra / Linear functions Difficulty: Hard

For the function f, if f of open parenthesis, 3 x, close parenthesis, equals x minus 6 for all values of x, what is the value of f of 6 ?

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Explanation

Choice B is correct. It’s given that f of 3 x, equals x minus 6 for all values of x. If 3 x equals 6, then f of 3 x will equal f of 6. Dividing both sides of 3 x equals 6 by 3 gives x equals 2. Therefore, substituting 2 for x in the given equation yields f of, open parenthesis, 3 times 2, close parenthesis, equals 2 minus 6, which can be rewritten as f of 6, equals negative 4.

Choice A is incorrect. This is the value of the constant in the given equation for f. Choice C is incorrect and may result from substituting x equals 6, rather than x equals 2, into the given equation. Choice D is incorrect. This is the value of x that yields f of 6 for the left-hand side of the given equation; it’s not the value of f of 6 .