\(P=\dfrac{1+19+\dfrac{19}{13}+\dfrac{19}{101}}{7+\dfrac{7}{13}+\dfrac{7}{19}+\dfrac{7}{101}}\)
\(=\dfrac{19\left(1+\dfrac{1}{3}+\dfrac{1}{19}+\dfrac{1}{101}\right)}{7\left(1+\dfrac{1}{13}+\dfrac{1}{19}+\dfrac{1}{101}\right)}=\dfrac{19}{7}\)
Tính:
\(\dfrac{7}{13}.\dfrac{5}{19}+\dfrac{7}{19}.\dfrac{8}{13}-3.\dfrac{7}{19}\)
Bài 4: so sánh biểu thức A và B
a) A=\(\dfrac{19}{41}+\dfrac{23}{53}+\dfrac{29}{61}\)
B=\(\dfrac{21}{41}+\dfrac{23}{49}+\dfrac{33}{65}\)
b) C=\(\dfrac{19^{20}+5}{19^{20}-8}vàD=\dfrac{19^{21}+6}{19^{21}-7}\)
\(\dfrac{14}{13}\) + (\(\dfrac{-1}{13}\) - \(\dfrac{19}{20}\))
\(\dfrac{3-\dfrac{3}{20}+\dfrac{3}{12}—\dfrac{3}{2013}}{7-\dfrac{7}{20}+\dfrac{7}{13}-\dfrac{7}{2013}}\)
4. tính
a. A=\(\dfrac{1}{3}\).\(\dfrac{4}{5}\)+\(\dfrac{1}{3}\).\(\dfrac{6}{5}\)+\(\dfrac{2}{3}\)
b. B=\(\dfrac{-5}{6}\).\(\dfrac{4}{19}\)+\(\dfrac{-7}{12}\).\(\dfrac{4}{19}\)-\(\dfrac{40}{57}\)
c. C=\(\dfrac{3}{7}\).\(\dfrac{9}{26}\)-\(\dfrac{1}{14}\).\(\dfrac{1}{13}\)-\(\dfrac{1}{7}\)
Chứng minh rằng: \(\dfrac{3}{2^2}+\dfrac{5}{6^2}+\dfrac{7}{12^2}+\dfrac{9}{20^2}+...+\dfrac{19}{90^2}< 1\)
Cho A = \(\dfrac{1}{5^2}+\dfrac{1}{6^2}+\dfrac{1}{7^2}+.....+\dfrac{1}{2019^2}\)
Chứng minh rằng \(\dfrac{20}{101}< A< \dfrac{1}{4}\)
sắp xếp các ps theo thứ tự giảm dần
\(\dfrac{-5}{8};\dfrac{7}{10};\dfrac{-16}{19};\dfrac{20}{23};\dfrac{214}{315};\dfrac{205}{107}\)
SS A và B
A=\(\dfrac{19}{24}-\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{7}{24}\)
B=\(\dfrac{7}{24}+\dfrac{5}{6}+\dfrac{1}{4}-\dfrac{3}{7}-\dfrac{5}{15}\)
