Question

помогите решить 11 . 12 в 12  u=1/6

Answer 1

11.
$b_{1}=496* frac{1}{2} =248$
$S_{6} = frac{ b_{1}( q^{6} -1)}{q-1}$
$S_{6} = frac{248 ( frac{1}{64}-1) }{- frac{1}{2} } = frac{248*63*2}{64} =488, 25$
12.
$frac{ q^{2}-4 v^{2} }{4vq} * frac{2}{q-2v} = frac{q+2v}{2qv}$
$frac{ frac{1}{5}+2* frac{1}{ 6} }{ 2*frac{1}{5}* frac{1}{6} } = frac{ frac{1}{5} + frac{1}{3} }{ frac{1}{15} }$
=$frac{8*15}{15*1} =8$

Answer 2

Спасибо)))

Answer 3

$b_{n}=496*( frac{1}{2}) ^{n}\\ b_{1}=496* frac{1}{2} =248\\ b_{6} =496*( frac{1}{2}) ^{6} =496* frac{1}{64} =7,75\\S _{6} = frac{ b_{6}*q- b_{1} }{q-1}\\ b_{6}= b_{1}* q^{5}\\ q^{5}= frac{ b_{6} }{ b_{1} }= frac{7,75}{248}=0,03125\\q= sqrt[5]{0,03125} =$$=0,5 S_{6}= frac{7,75*0,5-248}{0,5-1}= frac{3,875-248}{-0,5}=$$= frac{-244,125}{-0,5} =488,25\\\( frac{q}{4v}- frac{v}{q} )* frac{2}{q-2v}=$$= frac{ q^{2} -4 v^{2} }{4qv} * frac{2}{q-2v} = frac{(q-2v)(q+2v)}{2qv}* frac{1}{q-2v} = frac{q+2v}{2qv} = frac{ frac{1}{5}+2* frac{1}{6} }{2* frac{1}{5}* frac{1}{6} }= frac{ frac{1}{5}+ frac{1}{3} }{ frac{1}{15} }= frac{ frac{8}{15} }{ frac{1}{15}} =$$=8$