The value of ${\sum\limits_{r = 1}^{19} {\frac{{{}^{20}{C_{r + 1}}\left( { - 1} \right)}}{{{2^{2r + 1}}}}} ^r}$ is
The value of ${\sum\limits_{r = 1}^{19} {\frac{{{}^{20}{C_{r + 1}}\left( { - 1} \right)}}{{{2^{2r + 1}}}}} ^r}$ is
- A
$2\left( {{{\left( {\frac{3}{4}} \right)}^{20}} + 4} \right)$
- B
$-2\left( {{{\left( {\frac{3}{4}} \right)}^{20}} + 4} \right)$
- C
$2\left( {{{\left( {\frac{3}{4}} \right)}^{20}} - 4} \right)$
- D
$-2\left( {{{\left( {\frac{3}{4}} \right)}^{20}} - 4} \right)$
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- [IIT 1966]
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