sorry mk trả lời lại nè\(\dfrac{15\cdot\left(\dfrac{1}{6\cdot16}+\dfrac{1}{16\cdot26}+\dfrac{1}{26\cdot36}\right)}{33\cdot\left(\dfrac{1}{6\cdot16}+\dfrac{1}{16\cdot26}+\dfrac{1}{26\cdot36}\right)}=\dfrac{15}{33}\)
Tính phép tính sau:
\(\dfrac{33}{6.16}\)-\(\dfrac{63}{16.26}\)+\(\dfrac{93}{26.36}\)
Tính nhanh
\(B=\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}\)
1, \(\left(\dfrac{-1}{4}+\dfrac{7}{33}-\dfrac{5}{3}\right)-\left(\dfrac{15}{33}+\dfrac{6}{11}-\dfrac{48}{49}\right)\)
Bài 1:
\(a)5\dfrac{1}{20}+\dfrac{8}{9}-\dfrac{15}{25}+\dfrac{75}{-18}\)
\(b)\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}\)
\(c)\dfrac{6}{7}+\dfrac{5}{7}:5-\dfrac{8}{9}.\dfrac{6}{7}+\dfrac{5}{8}:5-\dfrac{3}{16}.\left(-2\right)^2\)
CMR:\(\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}+\dfrac{1}{195}< x+\dfrac{1}{30}\)
Chứng minh rằng:
S=\(\dfrac{1}{5}+\dfrac{1}{13}+\dfrac{1}{14}+\dfrac{1}{15}+\dfrac{1}{61}+\dfrac{1}{62}+\dfrac{1}{63}< \dfrac{1}{2}\)
\(\dfrac{1}{3}+\dfrac{13}{15}+\dfrac{33}{35}+...+\dfrac{9997}{9999}\)
tính nhanh
A=\(\dfrac{3}{2^2}.\dfrac{8}{3^2}.\dfrac{15}{4^2}...\dfrac{899}{30^2}\)
B=\(\dfrac{8}{9}.\dfrac{15}{16}.\dfrac{24}{25}...\dfrac{2499}{2500}\)
BT2: Tính nhanh
15) \(\left(\dfrac{1}{2}-\dfrac{13}{14}\right):\dfrac{5}{7}-\left(-\dfrac{2}{21}+\dfrac{1}{7}\right):\dfrac{5}{7}\)
16)\(\dfrac{3}{5}:\left(\dfrac{-1}{15}-\dfrac{1}{6}\right)+\dfrac{3}{5}:\left(\dfrac{-1}{3}-1\dfrac{1}{15}\right)\)
