The answer is:
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The GCF refers to the "greatest common factor".
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A factor of a number, or set of numbers, CANNOT be LARGER than either the number itself. The greatest common factor of a set of number cannot be larger than the smallest number within the particular set of numbers.
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The example given states that: "The GCF for 28, 42, 56 is 736." This not possible! The GCF cannot be highest than "28", which is the lowest number in the set of numbers given. The number "736" is MUCH larger than "28"; in fact, "736 is MUCH larger than ANY of the numbers in the entire set of numbers given.
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Also, the GCF for the set of numbers given; 28, 42, 56; is "14" ; NOT "736". So the GCF is not 736.
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