Question

1) Tính:

B=1+2+2^2+2^3+...+2^2008/1-2^2009

B=-9/10.5/14+1/10.(-9/2)+1/7.9-9/10)

S=3+3/2+3/2^2+...+3/2^9

A=1/30+1/42+1/56+1/72+1/90+1/110+1/132

2) Diền vào chỗ trống thich hợp ?giải thích?

-1/2<.../7<.../14<.../7<.../14<-1/7

 

 

Answer 1

A=\(\frac{1}{30}\)+\(\frac{1}{42}\)+\(\frac{1}{56}\)+\(\frac{1}{72}\)+\(\frac{1}{90}\)+\(\frac{1}{110}\)+\(\frac{1}{132}\)

A=\(\frac{1}{5.6}\)+\(\frac{1}{6.7}\)+\(\frac{1}{7.8}\)+\(\frac{1}{8.9}\)+\(\frac{1}{9.10}\)+\(\frac{1}{10.11}\)+\(\frac{1}{11.12}\)

A= \(\frac{1}{5}\)-\(\frac{1}{6}\)+\(\frac{1}{6}\)-\(\frac{1}{7}\)+\(\frac{1}{7}\)-\(\frac{1}{8}\)+\(\frac{1}{8}\)-\(\frac{1}{9}\)+\(\frac{1}{9}\)-\(\frac{1}{10}\)+\(\frac{1}{10}\)-\(\frac{1}{11}\)+\(\frac{1}{11}\)-\(\frac{1}{12}\)

A= \(\frac{1}{5}\)-\(\frac{1}{12}\)=\(\frac{7}{60}\)