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Mathematics 8 Online
OpenStudy (anonymous):

Binomial Theorem Ques!

OpenStudy (anonymous):

find coefficient of \[x^n\] in \[(1+x+x^2)^n\]

OpenStudy (ikram002p):

\(((1+x)+x^2)^n=\sum _{k=0}^n\binom{n}{k} (1+x)^{(n-k)}x^{2k}\)

OpenStudy (ikram002p):

\(\large ((1+x)+x^2)^n=\\\large \sum _{k=0}^n\binom{n}{k} \left ({\sum _{m=0}^{n-k}\binom{n-k}{m}x^{(m)}} \right )x^{2k}\)

OpenStudy (ikram002p):

first term when k=0 and m=n so \( \binom{n}{0} \binom{n}{0}x^{(n)}=x^n \)

OpenStudy (ikram002p):

second term when k=n/4 m=n/2 \(\binom{n}{\frac{n}{4}} \binom{\frac{4n-n}{4}}{\frac{n}{2}}x^{(n)}\)

OpenStudy (ikram002p):

so we would have \(\Huge (\binom{n}{\frac{n}{4}} \binom{\frac{4n-n}{4}}{\frac{n}{2}}+1) x^n\)

OpenStudy (anonymous):

i dont uderstand the notation you wrote under brackets if that means thsi then i gues it it correct \[1+ \frac{ n(n-1) }{ 1!}+\frac{ n(n-1)(n-2)(n-3) }{ (2!)^2 }...............\]

OpenStudy (ikram002p):

yes , it mean binomial coefficient

OpenStudy (anonymous):

can you explain this notation?i Dont know this

OpenStudy (ikram002p):

ok , could u please write what is binomial theorem ?

OpenStudy (anonymous):

\[(a+b)^n=\sum_{r=0}^{n} c_{r}^{n} a ^{n-r} \times b^r\]

OpenStudy (ikram002p):

oh ok :P so \( \binom{n}{r}=C_r^n\)

OpenStudy (ikram002p):

i used different notations only

OpenStudy (anonymous):

ohhk ty man life saver.

OpenStudy (ikram002p):

girl :P

OpenStudy (anonymous):

lol

OpenStudy (ikram002p):

so it would be \(1+C_{\frac{n}{4}}^n +C_{\frac{n}{2}}^\frac{4n-n}{4} \)

OpenStudy (sidsiddhartha):

this girl is not a ordinary girl :P

OpenStudy (ikram002p):

oh sry i made a typo \(1+C_{\frac{n}{4}}^n C_{\frac{n}{2}}^\frac{4n-n}{4}\)

OpenStudy (anonymous):

seriously. too Over powerful.

OpenStudy (ikram002p):

:P

OpenStudy (sidsiddhartha):

:3

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