How to Disprove a Nested Quantifier Expression?

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In summary, the conversation discusses a mathematical problem involving disproving an expression. It is clarified that the statement implies that for every possible y value, there exists an x value that, when multiplied by y, results in 1. The discussion then considers the domain of x and y and poses a question about a y-value that would make the statement false.
  • #1
albert1992
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I have trouble disproving the following expression

Screen Shot 2013-02-20 at 9.01.37 PM.png


I worded it as follows:

The product of certain number and every other nonzero number is 1
 
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  • #2
First of all, does the problem specify what the domain is for x and y?

To start, let's back things up a bit. In mathematical terms, the statement is as follows: There exists an x for every possible y value, such that if y isn't zero, when you choose an x-value, you can multiply it by every y-value in the domain, and the result is 1. So, assuming the domain is real numbers, for both x and y, let's try choosing a value for x:

Let x = 5. What value of y would make the statement true? y = 1/5. So, we've tested JUST ONE y-value. x = 5 has to work for EVERY single y. Can you think of a y-value that would make the statement false?EDIT: If anyone thinks my reply contains fallacious ideas, please inform me.
 
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  • #3
@Albert, has my reply stirred any thoughts in your mind?
 

FAQ: How to Disprove a Nested Quantifier Expression?

What is a nested quantifier?

A nested quantifier is a logical operator that is used in mathematical and logical expressions to describe the relationship between two or more quantified variables. In simple terms, it is a way of stating that one variable depends on another variable.

Why is it important to disprove nested quantifiers?

Disproving nested quantifiers is important because it allows us to determine the validity of a mathematical or logical statement. By showing that a statement with nested quantifiers is false, we can identify errors and inconsistencies in our reasoning and improve our understanding of the problem at hand.

How do you disprove a nested quantifier?

To disprove a nested quantifier, you can use counterexamples. This means finding specific values for the quantified variables that make the statement false. If you can show that the statement is false for even one set of values, then the statement is considered to be disproved.

What is the difference between disproving a nested quantifier and proving a statement?

Disproving a nested quantifier means showing that a statement is false for at least one set of values for the quantified variables. On the other hand, proving a statement means showing that the statement is true for all possible values of the quantified variables. In other words, disproving a nested quantifier is a way of testing the validity of a statement, while proving a statement is a way of demonstrating its truth.

Can nested quantifiers be used in all types of mathematical and logical statements?

Yes, nested quantifiers can be used in a wide variety of mathematical and logical statements. They are commonly used in statements involving sets, functions, and relations. However, it is important to note that not all statements with nested quantifiers can be disproved, as some may be true for all possible values of the quantified variables.

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