Question

x-\(\dfrac{20}{11.13}-\dfrac{20}{13.15}-\dfrac{20}{15.17}-...-\dfrac{20}{53.55}=\dfrac{3}{11}\)

A=\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{99.100}\)

\(\dfrac{-2}{3}\left|x\right|+1\dfrac{1}{2}=\dfrac{2}{5}\)

Answer 1

các bạn phại đổi kiểu chữ để làm bài này (VNI) , (TELEX)

Answer 2

vni

Answer 3

x - \(\dfrac{20}{11.13}-\dfrac{20}{13.15}-\dfrac{20}{15.17}-........-\dfrac{20}{53.55}=\dfrac{3}{11}\)

x - \(\left(\dfrac{20}{11.13}+\dfrac{20}{13.15}+\dfrac{20}{15.17}+...+\dfrac{20}{53.55}\right)=\dfrac{3}{11}\)

Đặt A = \(\dfrac{20}{11.13}+\dfrac{20}{13.15}+\dfrac{20}{15.17}+...+\dfrac{20}{53.55}\)

A = \(\dfrac{20}{2}\left(\dfrac{2}{11.13}+\dfrac{2}{13.15}+\dfrac{2}{15.17}+....+\dfrac{2}{53.55}\right)\)

A = \(\dfrac{20}{2}\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{17}+...+\dfrac{1}{53}-\dfrac{1}{55}\right)\)

A = \(10.\left(\dfrac{1}{11}-\dfrac{1}{55}\right)\)

A = 10 . 4/55

A = 8/11

TA Có : x - 8/11 = 3/11

x = 3/11 + 8/11

x = 11/11

x = 1

Vậy x = 1

Answer 4

A = \(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{99.100}\)

A = \(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}\)

A = \(\dfrac{1}{1}-\dfrac{1}{100}\)

A = 99/100

Answer 5

\(\dfrac{-2}{3}\left|x\right|+1\dfrac{1}{2}=\dfrac{2}{5}\)

\(\dfrac{-2}{3}\left|x\right|+\dfrac{3}{2}=\dfrac{2}{5}\)

\(\dfrac{-2}{3}\left|x\right|=\dfrac{2}{5}-\dfrac{3}{2}\)

\(\dfrac{-2}{3}\left|x\right|=\dfrac{-11}{10}\)

|x| = \(\dfrac{-11}{10}:\dfrac{-2}{3}\)

| x | = \(\dfrac{-33}{-20}=\dfrac{33}{20}\)

=> x = 33/20 hoặc x = -33/-20

Vậy.....

( mk ko chắc lắm )