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Mathematics 11 Online
OpenStudy (anonymous):

Binomial theorem

OpenStudy (anonymous):

If the 6th term in the expansion of \[\huge [\frac{ 1 }{ x ^{8/3}}+ x^2\log _{10}x]^8\] is 5600 , then find x

OpenStudy (anonymous):

I have attempted this question , it may take some minutes to post

ganeshie8 (ganeshie8):

\(k\) th term of \((a+b)^n\) : \[\binom{n}{\color{red}{k-1}} a^{n-(\color{Red}{k-1})} b^{\color{Red}{k-1}}\]

ganeshie8 (ganeshie8):

\(6\) th term of \((a+b)^8\) : \[\binom{8}{\color{red}{6-1}} a^{8-(\color{Red}{6-1})} b^{\color{Red}{6-1}}\]

OpenStudy (anonymous):

\[\huge \left(\begin{matrix}8 \\ 5\end{matrix}\right) x ^{\frac{ -512 }{ 27 }}.(x ^{2}\log _{10}x)^{5}\]=5600

OpenStudy (anonymous):

\[\huge x ^{\frac{ -512 }{ 27 }}.(x ^{2}\log _{10}x)^{5} = 100\]

ganeshie8 (ganeshie8):

doesn't look correct

ganeshie8 (ganeshie8):

how did you get \(\large x^{\frac{-512}{27}}\) ?

OpenStudy (anonymous):

yeah i felt i was making a terrible mistake somewhere

ganeshie8 (ganeshie8):

yes a very silly mistake actually

OpenStudy (anonymous):

hmm, x^{-8/3}^3

ganeshie8 (ganeshie8):

\[\large \left(a^m\right)^n = a^{m\times n}\]

OpenStudy (anonymous):

-_- sry

ganeshie8 (ganeshie8):

\[\left(x^{-8/3}\right)^3 = x^{-8/3\times 3} = x^{-8}\]

OpenStudy (anonymous):

\[\huge x ^{-8}.(x ^{2}\log _{10}x)^{5}=100\]

ganeshie8 (ganeshie8):

you should end up with \[\large x ^{-8}\cdot (x ^{2}\log _{10}x)^{5} = 100\]

OpenStudy (anonymous):

it is a equation now i can solve that , thank you

ganeshie8 (ganeshie8):

careful, it looks tricky...

OpenStudy (anonymous):

\[\huge x^{2} . \log ^{5}_{10}x = 100\]

OpenStudy (anonymous):

its a multiple choice , so by trial and error i got 10 hmm how to do that subjectively

ganeshie8 (ganeshie8):

that looks good

ganeshie8 (ganeshie8):

x=10 makes the log thingy 1 and balances both sides so yeah..

OpenStudy (anonymous):

so if it was a subjective paper how would we solve that

ganeshie8 (ganeshie8):

idk but it would be painful im sure

OpenStudy (perl):

subjective paper?

OpenStudy (anonymous):

yeah any method is not visible to me not subjective paper

ganeshie8 (ganeshie8):

he wants to solve it analytically @perl

OpenStudy (perl):

oh :)

OpenStudy (anonymous):

but its good to know methods , my logarithm will also be revised

OpenStudy (anonymous):

i think i got it

ganeshie8 (ganeshie8):

show me how

OpenStudy (anonymous):

no it isn't working well

OpenStudy (anonymous):

I will post it as a new question

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