a)\(\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{9}{45}\\ =\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{1}{5}\\ =\dfrac{14-15+1}{35}\\ =\dfrac{0}{35}=0\)
b)\(\dfrac{5}{15}+\dfrac{14}{25}-\dfrac{12}{9}+\dfrac{2}{7}+\dfrac{11}{25}\\ =\left(\dfrac{1}{3}-\dfrac{4}{3}\right)+\left(\dfrac{14}{25}+\dfrac{11}{25}\right)+\dfrac{2}{7}\\ =-1+1+\dfrac{2}{7}\\ =0+\dfrac{2}{7}=\dfrac{2}{7}\)
1. thực hiện phép tính
a. \(\dfrac{11}{21}\)+\(\dfrac{-4}{7}\)
b. \(\dfrac{5}{15}\)+\(\dfrac{14}{25}\)-\(\dfrac{12}{9}\)+\(\dfrac{2}{7}\)+\(\dfrac{11}{25}\)
c. \(\dfrac{2}{3}\)+\(\dfrac{5}{7}\)-\(\dfrac{3}{14}\)
d. \(\dfrac{2}{5}\)-\(\dfrac{3}{7}\)+\(\dfrac{9}{45}\)
e.\(\dfrac{21}{47}\)+\(\dfrac{9}{45}\)+\(\dfrac{26}{47}\)+\(\dfrac{45}{5}\)
f. \(\dfrac{15}{12}\)-\(\dfrac{18}{13}\)+\(\dfrac{5}{13}\)-\(\dfrac{3}{12}\)
g. \(\dfrac{-8}{18}\)-\(\dfrac{15}{27}\)
h.\(\dfrac{3}{7}\)+\(\dfrac{-5}{2}\)-\(\dfrac{3}{5}\)
i.(\(\dfrac{11}{12}\):\(\dfrac{33}{16}\)).\(\dfrac{3}{5}\)
a) \(\left(7\dfrac{4}{9}+3\dfrac{7}{11}\right)-3\dfrac{4}{9}\)
b) \(5\dfrac{2}{7}\cdot\dfrac{8}{11}+5\dfrac{2}{7}\cdot\dfrac{5}{11}-5\dfrac{2}{7}\cdot\dfrac{2}{11}\)
c) \(1\dfrac{13}{15}\cdot0,75-\left(\dfrac{11}{20}+25\%\right):\dfrac{7}{5}\)
Giúp mình nha
Đang cần gấp
2. thực hiện phép tính
a. \(\dfrac{3}{4}\)+\(\dfrac{3}{5}\)-\(\dfrac{18}{60}\)
b. \(\dfrac{17}{8}\)-\(\dfrac{11}{6}\)-\(\dfrac{2}{9}\)
c. \(\dfrac{20}{45}\)+\(\dfrac{14}{35}\)+\(\dfrac{32}{44}\)
d.\(\dfrac{23}{29}\)+\(\dfrac{5}{11}\)+\(\dfrac{17}{11}\)
e.\(17\dfrac{25}{27}\)+\(3\dfrac{7}{2}\)
Các bạn giúp với :<
Bài 1:
a, CMR: A = \(\dfrac{3}{1^2.2^2}+\dfrac{5}{2^2.3^2}+\dfrac{7}{3^2.4^2}+...+\dfrac{21}{10^2.11^2}< 1\)
b, Cho B = \(\dfrac{3}{4}+\dfrac{8}{9}+\dfrac{15}{16}+\dfrac{24}{25}+...+\dfrac{2499}{2500}.\) CMR: B không phải là số nguyên.
c, So sánh: C = \(\dfrac{2}{2^1}+\dfrac{3}{2^2}+\dfrac{4}{2^3}+...+\dfrac{2021}{2^{2020}}\) với 3.
Bài1. (4điểm) Thực hiện phép tính:
a) \(A=\dfrac{3}{5}+6\dfrac{5}{6}\left(11\dfrac{5}{20}-9\dfrac{1}{4}\right):8\dfrac{1}{3}\)
b) \(B=\dfrac{-1}{2}+\dfrac{-1}{6}+\dfrac{-1}{12}+\dfrac{-1}{20}+\dfrac{-1}{30}+\dfrac{-1}{42}+\dfrac{-1}{56}+\dfrac{-1}{72}+\dfrac{-1}{90}\)
a,\(\dfrac{-5}{9}\)+\(\dfrac{5}{9}\):(1\(\dfrac{2}{3}\)-2\(\dfrac{1}{12}\))
b,\(\dfrac{-7}{25}\).\(\dfrac{11}{13}\)+\(\dfrac{-7}{25}\).\(\dfrac{2}{13}\)-\(\dfrac{18}{25}\)
c,(\(\dfrac{5}{7}\).0,6-5:3\(\dfrac{1}{2}\)).(40%-1,4).\(\left(-2\right)^3\)
Tính nhanh:
\(B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)
Thực hiện phép tính 1 cách hợp lý
\(\dfrac{0,8:\left(\dfrac{4}{5}.1.25\right)}{0,64-\dfrac{1}{25}}+\dfrac{\left(1,08-\dfrac{2}{25}\right):\dfrac{4}{7}}{\left(6\dfrac{5}{9}-3\dfrac{1}{4}\right).2\dfrac{2}{17}}\)
1. tính
a. \(\dfrac{3}{5}\)-\(\dfrac{2}{3}\)+\(\dfrac{16}{15}\)
b. (\(\dfrac{5}{6}\)-\(\dfrac{4}{5}\)):\(\dfrac{7}{30}\)-\(\dfrac{6}{7}\)
c. \(\dfrac{4}{11}\).\(\dfrac{-2}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{-8}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{1}{9}\)
d.\(\dfrac{-13}{10}\)-\(\dfrac{15}{16}\):\(\dfrac{-3}{4}\)+\(\dfrac{21}{25}\).\(\dfrac{-15}{28}\)
