#Proof Question On Sets

55 messages · Page 1 of 1 (latest)

stray spindle
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I was struggling on question number 3 in the attached image. I found (an) answer but I don't believe it is correct because my professor stated that our proof should end with 2^(n-1)*k^n multiplied by 2. I am not sure where I am going wrong or how to get that.

wheat flumeBOT
stray spindle
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Also my answer was (4k)^n and i dont think it is appropiate to say that exists in 2Z directly

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I think I need more proof between that and x^n exists in 2Z

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but I am not sure what

pallid meteor
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x^n = (2k)^n

stray spindle
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I did it again and got that x^n=2^n*k^n

pallid meteor
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yeah

stray spindle
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but im confused on how that helps me

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can i say that x^n*k^n exists in 2Z

pallid meteor
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separates a 2

stray spindle
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so I would end my proof with (2x)^n exists in 2Z?

pallid meteor
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$$x^n=2* (2^{n-1}*k^n)$$

undone hullBOT
stray spindle
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I'm a little bit confused on how to get there

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I think I am missing a step

pallid meteor
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do you know how to get x^n=2^n*k^n?

stray spindle
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yes

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My works kinda all over the place but I think I did it

pallid meteor
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if x=2k F1
then x^n = (2k)^n

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sustitution

stray spindle
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So I would set the left side equal to (2k)^n? and then solve?

pallid meteor
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No, we leave x^n because that's what we're trying to prove

stray spindle
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What is the substitution for then? Am I plugging it into k^n and pulling a two out of both terms>

pallid meteor
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Would be like:
x^n =x^n
x^n = (2k)^n sustitution

stray spindle
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so is my current work wrong then?

pallid meteor
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I think it is or maybe you just took too many steps.

stray spindle
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because rn I am at x^n=2^n*k^n

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and i dont understand how to get from there to what we are trying to get

pallid meteor
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like in F2 2^a*2^b =2^(a+b)

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but the other way around, instead of putting together and adding them, we are going to separate them and subtract

stray spindle
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I saw that to get n-1 in the exponent for two

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but I was confused on how to keep k^n

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cuz if i undistrube a 2 in this equation doesnt that make the k^n not k^n

pallid meteor
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We don't need to factor, everything is multiplying.
That would be if we were adding

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2^2 *4 =2*(2*4) =16
not 2*(2*4/2) = 8

stray spindle
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oh my god im stupid i see it now

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thank you

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i really appreciate it

pallid meteor
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although it doesn't really matter if we change k, the important thing is that it has the form of 2*(something)

stray spindle
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isee

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that makes sense

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then 2(2^(n-1)*k^n) exists in 2Z because it is in the form of 2(smth)

pallid meteor
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yeah

stray spindle
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okay thank you!

astral heath
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x=2k

//because n is a Natural number)
2^(n-1) is an integer
k^n is an integer
[2^(n-1) * k^n] is an integer

x^n = (2k)^n= 2^n * k^n = 2[2^(n-1) * k^n]
2^n * k^n is an even integer

stray spindle
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I was looking at my assignment and just realized I had to format it a specific way so I ended up with this

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and I am not sure how to end it

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I haven't used F4 so I assume it has something to do with F4 but I don't see how that validates the statement

astral heath
stray spindle
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Oops yeah I fixed it haha

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Thank you

wheat flumeBOT
stray spindle
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.close