What is the coefficient of x^6 in the expansion (1+x+x^2)^9. Explain please
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Originally Posted by ranyeng What is the coefficient of x^6 in the expansion (1+x+x^2)^9. Explain please Count the number of ways to rearrange each of these string. For example: the string can be rearranged in ways. Note that product is . The sum of the numbers of rearrangements is the coefficient of .
Last edited by Plato; Apr 6th 2010 at 12:59 PM.
Can you please explain with the above example( better if you write the steps)
Originally Posted by ranyeng Can you please explain with the above example( better if you write the steps) No sorry that happens to be your job. I will say the number of ways to rearrange the string is . If you do not understand that rule, then you have no business trying this question.
Originally Posted by ranyeng What is the coefficient of x^6 in the expansion (1+x+x^2)^9. Explain please Another approach is to make use of the identity then expand and by the binomial theorem. (Assuming you know how to use the binomial theorem for negative exponents.)
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