Question 1042916
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Don't know how to this equation.. can someone help me?
Solve the following equation for n

nC2 - 5{P(1/3n, 2)} + 1/3n = 9
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n = 9.



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<U>Comment from student</U>: Thanks a lot ikleyn!! Can you give me the steps on how you found nine please. So that I can understand better.
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<pre>
It is clear that {{{(1/3)*n}}} must be integer positive.

Therefore, let us introduce new variable m = {{{(1/3)n}}}.

Then n = 3m,  and the equation takes the form

(3m)C2 - 5P(m,2) + m = 9.

Or  {{{(3m*(3m-1))/2}}} - 5*m*(m-1) + m = 9.

This is a quadratic equation, and you can solve it.
</pre>