JEE MATHEMATICS MCQ: BINOMIAL THEOREM

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Application +4 | -1

\sum\limits_{{r=0}}^n r\left(\begin{array}{l}n \\ r\end{array}\right)\left(\frac{2}{7}\right)^r\left(\frac{5}{7}\right)^{n-r}=

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Correct option: C

\frac{2 n}{7}

Option C (

\frac{{2 n}}{{7}}

) is correct because it is derived from differentiating the binomial expansion and substituting the given values.

More Questions from BINOMIAL THEOREM

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\left({ }^{10} C_0\right)^2-\left({ }^{10} C_1\right)^2+\ldots-\left({ }^{10} C_9\right)^2+\left({ }^{10} C_{10}\right)^2

a

d

\left( {n + 1} \right)

a{C_0} - \left( {a + d} \right){C_1} + \left( {a + 2d} \right){C_2} - ... + ...

(1-x)^{201}\left(1+x+x^2\right)^{200}

\left(\frac{1}{x}+2 x\right)^n

{x^5}

\frac{{1 + {x^2}}}{{1 + x}},\left| x \right| < 1,

\left(\begin{array}{c}2 n+1 \\ 0\end{array}\right)+\left(\begin{array}{c}2 n+1 \\ 3\end{array}\right)+\left(\begin{array}{c}2 n+1 \\ 6\end{array}\right)+\ldots=170

n