1962 AHSME Problems/Problem 12: Difference between revisions
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==Solution== | ==Solution== | ||
{{ | This is equivalent to <math>\frac{(a-1)^6}{a^6}.</math> | ||
Its expansion has 7 terms, whose coefficients are the same as those of <math>(a-1)^6</math>. | |||
By the Binomial Theorem, the sum of the last three coefficients is | |||
<math>\binom{6}{2}-\binom{6}{1}+\binom{6}{0}=15-6+1=\boxed{10 \textbf{ (C)}}</math>. | |||
Revision as of 12:20, 16 April 2014
Problem
When 
is expanded the sum of the last three coefficients is:
Solution
This is equivalent to 
Its expansion has 7 terms, whose coefficients are the same as those of 
.
By the Binomial Theorem, the sum of the last three coefficients is
.
