Algebra

What is the sum of the coefficients in the expansion of ( 1 + x ) 5 (1+x)^{5} ?


The answer is 32.

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2 solutions

Finn Hulse
Apr 18, 2014

Remember the Binomial Expansion Theorem and it's relationship to Pascal's Triangle. The n n th column will have a total sum of 2 n 1 2^{n-1} . Of course, the first column adds simply to 1 1 . For the expansion, the sum will thus be 2 5 2^5 which is 32 \boxed{32} . :D

Exactly what I got! @Finn Hulse :D

Elliott Macneil - 7 years, 1 month ago

easy one ............................

math man - 6 years, 9 months ago

n = 0 5 ( 5 n ) = ( 5 0 ) + ( 5 1 ) + ( 5 2 ) + ( 5 3 ) + ( 5 4 ) + ( 5 5 ) = 2 ( 1 + 5 + 10 ) = 32 \large\displaystyle \sum _{n=0}^{5} \dbinom{5}{n}=\dbinom{5}{0}+\dbinom{5}{1}+\dbinom{5}{2}+\dbinom{5}{3}+\dbinom{5}{4}+\dbinom{5}{5}=2(1+5+10)=32

Complicated way to solve such an easy problem lol @Páll Márton

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