How many subsets are in {∅} and {0}?

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The discussion clarifies the number of subsets for the sets {∅} and {0}. The set {∅} has two subsets: the empty set (∅) and the set itself ({∅}), which are distinct. Similarly, the set {0} also has two subsets: ∅ and {0}. It emphasizes the importance of understanding the difference between the empty set and a set containing the empty set as an element. Overall, both sets have two subsets, demonstrating a fundamental concept in set theory.
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For ##{∅}##, I've come to the conclusion that there is only one subset because it has the empty set and itself as subsets. In this case, there are the same thing.

For ##{0}##, there should be two subsets; the empty set and the set itself.

Am I right?
 
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##\{\emptyset\}## has ##\emptyset## and ##\{\emptyset\}## as subsets and they are not equal. So you are not correct.
 
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Math_QED said:
##\{\emptyset\}## has ##\emptyset## and ##\{\emptyset\}## as subsets and they are not equal. So you are not correct.
I see. There are two subsets; ##∅##, and the subset itself.
 
angela107 said:
I see. There are two subsets; ##∅##, and the subset itself.
This is an example where you must think logically rather than practically. There is a difference between "the empty set", denoted by ##\emptyset## and "the set containing the empty set as the only element", denoted by ##\{\emptyset \}##.

A non-mathematician might claim that in both cases you have precisely nothing. But, mathematically, they are not the same thing.
 
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In both cases you hve a set with one element, hence there are two subsets, the subset containing that element and the one not containing it. It does not matter what the element is.
 
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Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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