SOLUTION: Explain why the product of a nonzero rational number and an irrational number is irrational

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Question 654623: Explain why the product of a nonzero rational number and an irrational number is irrational
Answer by solver91311(24713) About Me  (Show Source):
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Let represent the set of irrational numbers.

Assume that for some and that

Then



by definition of rationals.

Is it possible then that the product of and is rational, that is

But that means



But since are all integers and the integers are closed under multiplication, must be rational since it is the quotient of integers, contradicting the original assumption that it was irrational.

Therefore, reductio ad absurdum, the product of a non-zero rational number and an irrational number cannot be rational. Q.E.D.

John

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