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$\sum_{i=1}^{x} x + \sum_{i=1}^{x} 2 = 8$

Trying to discover $x$ here, so I made: $x(x-1) + 2(x-1) = 8$

Which should give me the $x$, but instead of an integer I get: $x = \frac{-1\pm\sqrt{41}}{2}$

When the answer should be $x=2$, according to the solution.

What am I doing wrong?

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    Thank you everyone for the insight, I'm trying to get better at math :)) It's all right now.2010-10-31

1 Answers 1

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You have $x$ integers between $1$ and $x$. Look: $1, 2, 3, \ldots, x-1, x$. So you are just not counting properly.