Question

Giúp dới làm ơn nhanh nhất có thể nha (＠´ー`)ﾉﾞ

Answer 1

câu d thôi :)

= 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + .... + 1/9 - 1/10

= 1/2 - 1/10

= 4/10 = 2/5

Answer 2

;-; ko sao dù so cũng cảm ơn

Answer 3

\(c,\dfrac{11}{2}.\dfrac{8}{15}+\dfrac{8}{15}.\dfrac{-5}{2}\\ =\dfrac{8}{15}\left(\dfrac{11}{2}+\dfrac{-5}{2}\right)\\ =\dfrac{8}{15}.\dfrac{6}{2}\\ =\dfrac{8}{15}.3\\ =\dfrac{8}{5}\\ d,\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{9.10}\\ =\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\\ =\dfrac{1}{2}-\dfrac{1}{10}\\ =\dfrac{5}{10}-\dfrac{1}{10}\\ =\dfrac{4}{10}\\ =\dfrac{2}{5}\)