Find the coefficients of in the expansion of

My attempt:

to obtain , coefficients of and have to be used.

therefore,

OR

Puzzled at arriving at for .

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- Apr 17th 2010, 07:21 AMPunchBinomial expansion
Find the coefficients of in the expansion of

My attempt:

to obtain , coefficients of and have to be used.

therefore,

OR

Puzzled at arriving at for . - Apr 17th 2010, 07:39 AMmathaddict
- Apr 17th 2010, 06:43 PMPunch
- Apr 17th 2010, 10:35 PMmathaddict
Great . Of course , we can expand the whole thing and combine terms which will produce x^7 but it would be tedious and risky so its better to use the binomial theorem :

so now lets see what values of k give 7

14-3k=7 , k=7/3 and this cant be since k must be +ve integer

how about 16-3k=7 , k=3 . (Nod)

its coefficient is - Apr 18th 2010, 02:12 AMPunch
I didnt quite understand "so now lets see what values of k give 7

14-3k=7 , k=7/3 and this cant be since k must be +ve integer

how about 16-3k=7 , k=3 ."

Does this shows that if the value of r is not a whole number, we have to round the number off and see if the power of x is what we are after? - Apr 18th 2010, 02:45 AMArchie Meade
- Apr 18th 2010, 05:53 AMPunch
alright so can i conclude that I only have to use the term coefficient of x^5 since there is no x^7 term

- Apr 18th 2010, 07:33 AMArchie Meade