Answer: A) 6 and B) 28
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Step-by-step explanation:
By definition, a perfect number is one where the factors smaller than itself add to the number in question.
The factors of 6, smaller than 6, are {1,2,3}. We can see that 1+2+3 = 6. Therefore, 6 is a perfect number.
Similarly, 1+2+4+7+14 = 28 showing that 28 is also a perfect number.
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The factors of 625, that are smaller than 625, are 1,5,25,125. They add to 1+5+25+125 = 156. This isn't equal to 625, so 625 isn't a perfect number.
A similar issue happens with 100 as well. The smaller factors are 1,2,4,5,10,20,25,50, meaning we get a sum of 1+2+4+5+10+20+25+50 = 117, which is too large.
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The first four perfect numbers are: {6, 28, 496, 8128}