Question

X/2018-1/70-1/15-1/21-...-1/120=5/8

(11/12+11/12.23+11/23.34+....+2/89.100)+x=5/3

(2'11.13+2/13.15+...+2/19.21)-x+4+221/231=7/3

Answer 1

b: \(\Leftrightarrow1-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{34}+...+\dfrac{1}{89}-\dfrac{1}{100}+x=\dfrac{5}{3}\)

=>x+99/100=5/3

=>x=5/3-99/100=203/300

c: \(\Leftrightarrow\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)-x+4+\dfrac{221}{231}=\dfrac{7}{3}\)

\(\Leftrightarrow\dfrac{10}{231}-x+4+\dfrac{221}{231}=\dfrac{7}{3}\)

=>5-x=7/3

hay x=8/3