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Mathematics 14 Online
OpenStudy (anonymous):

Find a counterexample for the statement. For every real number N > 0, there is some real number x such that Nx > x.

OpenStudy (perl):

N=1

OpenStudy (anonymous):

for any number \[0<N<1\]

OpenStudy (anonymous):

yes in fact\[0<N\le1\]

OpenStudy (perl):

I enjoyed this problem immensely :)

OpenStudy (perl):

also you might want to first write the negation of the statement before finding the counterexample!!!!

OpenStudy (perl):

Statement: For every real number N > 0, there is some real number x such that Nx > x. Negation : There exists a real number N>0 such that for all real numbers x it is true that Nx <= x

OpenStudy (perl):

and any N in (0,1] works

OpenStudy (perl):

the negation *is* a counterexample, so proving the negation is finding at least one N :)

OpenStudy (anonymous):

I have a feeling @malia667 didnt write the equation exactly asked. It is missig some absolute value symbols!!!

OpenStudy (perl):

electro, can you show me where you would need an absolute value?

OpenStudy (anonymous):

thanks guys :)) n=1 was correct

OpenStudy (anonymous):

more to come

OpenStudy (anonymous):

\[|Nx|>|x|\] since x is any real number, it could be negative too

OpenStudy (perl):

it doesnt matter if x is negative

OpenStudy (anonymous):

\[5(-3)<-3\]

OpenStudy (anonymous):

N=5 and x=-3 the inequality flips

OpenStudy (perl):

.yes but the counterexample addresses that

OpenStudy (anonymous):

it may but there are infinite answers. the question would have no meaning to it

OpenStudy (perl):

it is true that for all x, Nx > x for N inside (0,1]

OpenStudy (anonymous):

the given inequality is false for each and every N

OpenStudy (anonymous):

i need to ask another question please :))

OpenStudy (anonymous):

it you put an absolute sign, then it'd make sense

OpenStudy (anonymous):

yes so the above claim goes wrong too when x<0

OpenStudy (perl):

no, because it says 'there exists an x '

OpenStudy (perl):

it didnt say for all x in the original statement

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