Question

giúp mình với!

x-20/11.13-20/13.15-20/15.17-...-20/53.55=3/11

Answer 1

=> x- (\(\frac{20}{11.13}\) + \(\frac{20}{13.15}\) +...+ \(\frac{20}{53.55}\)) = \(\frac{3}{11}\)

=> x - 10.(\(\frac{2}{11.13}\) + \(\frac{2}{13.15}\) +...+ \(\frac{2}{53.55}\)) = \(\frac{3}{11}\)

=> x - 10.( \(\frac{1}{11}\) - \(\frac{1}{13}\) + \(\frac{1}{13}\) -  \(\frac{1}{15}\) +...+ \(\frac{1}{53}\) - \(\frac{1}{55}\)) = \(\frac{3}{11}\)

=> x - 10. (\(\frac{1}{11}\) - \(\frac{1}{55}\)) = \(\frac{3}{11}\)

=> x - 10.\(\frac{4}{55}\) = \(\frac{3}{11}\) 

=> x - \(\frac{8}{11}\) = \(\frac{3}{11}\)=> x=1 Vậy x=1

Answer 2

giải được xin cảm ơn

Answer 3

thank you

Answer 4

1/2²+1/3²+1/4²+1/5²+1/6²+1/7²+1/8²<1

Answer 5

Ta có

\(Đăt\)  \(M=-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}\)

                     \(=10\left(\frac{2}{11.13}-\frac{2}{13.15}-...-\frac{2}{53.55}\right)\)

                    \(=10\left(-\frac{1}{11}+\frac{1}{13}-\frac{1}{13}+\frac{1}{15}-...-\frac{1}{53}+\frac{1}{55}\right)\)

                    \(=10\left(-\frac{1}{11}+\frac{1}{55}\right)=\frac{-40}{55}\)

Thê M vào bt có

          \(x-\frac{-40}{55}=\frac{3}{11}\)

                                 còn lại tự giải

Answer 6

TL:

x=1

-HT-