Pving parameters of perfect cubes and squares

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frosh14
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Pving parameters of perfect cubes and squares

Unread post by frosh14 » Mon Jul 04, 2011 5:15 am

Show that there are no positive integers n for which $n^4 + 2n^3 + 2n^2 + 2n + 1$ is a perfect
square. Are there any positive integers $n$ for which $n^4 + n^3 + n^2 + n + 1$ is a perfect square?
If so, find all such $n$.
Last edited by Masum on Sat Jul 16, 2011 11:02 pm, edited 1 time in total.
Reason: You can very easily use LaTeX

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Moon
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Re: Pving parameters of perfect cubes and squares

Unread post by Moon » Mon Jul 04, 2011 11:06 pm

Hint:
Try to show that $n^4 + 2n^3 + 2n^2 + 2n + 1 $ lies between two consecutive squares.
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Tahmid Hasan
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Re: Pving parameters of perfect cubes and squares

Unread post by Tahmid Hasan » Tue Jul 05, 2011 11:49 am

1.$n^4<n^4 + 2n^3+2n^2+2n+1<(n+1)^4$
the second problem can be solved in the same way.
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nayel
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Re: Pving parameters of perfect cubes and squares

Unread post by nayel » Tue Jul 05, 2011 4:45 pm

Tahmid Hasan wrote:1.$n^4<n^4 + 2n^3+2n^2+2n+1<(n+1)^4$
the second problem can be solved in the same way.
There can be perfect squares between two consecutive fourth powers, e.g. $1^4<2^2<2^4$.
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Tahmid Hasan
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Re: Pving parameters of perfect cubes and squares

Unread post by Tahmid Hasan » Wed Jul 06, 2011 11:53 am

sorry for my miscalculation :(,here's the right one
$(n^2+n)^2<n^4+2n^3+2n^2+2n+1<(n^2+n+1)^2$
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