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20 tháng 7 2018
1. 25 : 5,7 = 250/57
2. 30:2.8.4 = 480
3. 20:2^2.14= 70
4. 125:5^3.170= 170
5. 64:2^5.30.4=240
6. (25:5^2.30): 15.7=14
bạn à! Nhiều quá mình ko làm hết được. sorry nha.^-^
HP
15 tháng 4 2018
a, \(\dfrac{5}{1.3}\)+\(\dfrac{5}{3.5}\)+\(\dfrac{5}{5.7}\)+...+\(\dfrac{5}{99.101}\)
= 5.\(\dfrac{1}{1.3}\)+5.\(\dfrac{1}{3.5}\)+5.\(\dfrac{1}{5.7}\)+...+5.\(\dfrac{1}{99.101}\)
=5.(\(\dfrac{1}{1.3}\)+\(\dfrac{1}{3.5}\)+\(\dfrac{1}{5.7}\)+...+\(\dfrac{1}{99.101}\))
=5.(\(\dfrac{2}{2}\).\(\dfrac{1}{1.3}\)+\(\dfrac{2}{2}\).\(\dfrac{1}{3.5}\)+\(\dfrac{2}{2}\).\(\dfrac{1}{5.7}\)+...+\(\dfrac{2}{2}\).\(\dfrac{1}{99.101}\))
=\(\dfrac{5}{2}\).(\(\dfrac{2}{1.3}\)+\(\dfrac{2}{3.5}\)+\(\dfrac{2}{5.7}\)+...+\(\dfrac{2}{99.101}\))
=\(\dfrac{5}{2}\).(\(\dfrac{1}{1}\)-\(\dfrac{1}{3}\)+\(\dfrac{1}{3}\)-\(\dfrac{1}{5}\)+\(\dfrac{1}{5}\)-\(\dfrac{1}{7}\)+...+\(\dfrac{1}{99}\)-\(\dfrac{1}{101}\))
=\(\dfrac{5}{2}\).(\(\dfrac{1}{1}\)-\(\dfrac{1}{101}\))
=\(\dfrac{5}{2}\).\(\dfrac{100}{101}\)
=\(\dfrac{250}{101}\)
=\(2\dfrac{48}{101}\)
b,\(\dfrac{-11}{23}\).\(\dfrac{6}{7}\)+\(\dfrac{8}{7}\).\(\dfrac{-11}{23}\)-\(\dfrac{1}{23}\)
=\(\dfrac{-11}{23}\).(\(\dfrac{6}{7}\)+\(\dfrac{8}{7}\))-\(\dfrac{1}{23}\)
=\(\dfrac{-11}{23}\).2-\(\dfrac{1}{23}\)
=\(\dfrac{-22}{23}\)-\(\dfrac{1}{23}\)
=-1
c,\(\dfrac{2.3}{7}\)+(\(\dfrac{2}{9}\)-\(1\dfrac{1}{3}\))-\(\dfrac{5}{3}\):\(\dfrac{1}{9}\)
=\(\dfrac{6}{7}\)+(\(\dfrac{2}{9}\)-\(\dfrac{4}{3}\))-\(\dfrac{5}{3}\).9
=\(\dfrac{6}{7}\)-\(\dfrac{10}{9}\)-\(\dfrac{5}{3}\).9
=\(\dfrac{6}{7}\)-\(\dfrac{10}{9}\)-15
=\(\dfrac{54}{63}\)-\(\dfrac{70}{63}\)-\(\dfrac{945}{63}\)
=\(\dfrac{-961}{63}\)=\(-15\dfrac{16}{63}\)
d,(20+\(9\dfrac{1}{4}\)):\(2\dfrac{1}{4}\)
=(20+\(\dfrac{37}{4}\)):\(\dfrac{9}{4}\)
=20:\(\dfrac{9}{4}\)+\(\dfrac{37}{4}\):\(\dfrac{9}{4}\)
=20.\(\dfrac{4}{9}\)+\(\dfrac{37}{4}\).\(\dfrac{4}{9}\)
=\(\dfrac{80}{9}\)+\(\dfrac{37}{9}\)
=\(\dfrac{117}{9}\)
Mình làm nhiều như thế thì sẽ không tránh được lỗi sai nên mình mong bạn hãy xem lại thật kĩ nhé!
16 tháng 2 2018
bài 1.
A) \(\dfrac{-5}{9}+\dfrac{3}{5}-\dfrac{3}{9}+\dfrac{-2}{5}=\left(\dfrac{-5}{9}-\dfrac{3}{9}\right)+\left(\dfrac{3}{5}+\dfrac{-2}{5}\right)=\dfrac{-8}{9}+\dfrac{1}{5}=-\dfrac{31}{45}\)
B)\(-\dfrac{5}{13}+\left(\dfrac{3}{5}+\dfrac{3}{1}-\dfrac{4}{10}\right)=-\dfrac{5}{13}+3+\left(\dfrac{3}{5}-\dfrac{4}{10}\right)=-\dfrac{5+3.13}{13}+\dfrac{1}{5}=-\dfrac{207}{65}\)C)\(\dfrac{5}{17}-\dfrac{9}{15}-\dfrac{2}{-17}+\dfrac{-3}{15}=\left(\dfrac{5}{17}+\dfrac{2}{17}\right)+\left(\dfrac{-9}{15}+\dfrac{-3}{15}\right)=\dfrac{7}{17}-\dfrac{12}{15}=-\dfrac{33}{85}\)D)\(\left(\dfrac{1}{9}-\dfrac{9}{17}\right)+\dfrac{3}{6}-\left(\dfrac{12}{17}-\dfrac{1}{2}\right)+\dfrac{-1}{9}=\left(\dfrac{1}{9}+\dfrac{-1}{9}\right)+\left(\dfrac{3}{6}+\dfrac{1}{2}\right)-\dfrac{12}{17}=1-\dfrac{12}{17}=\dfrac{5}{17}\)
10 tháng 4 2016
\(\frac{2,3}{7}+\left(\frac{2}{9}-\frac{10}{7}\right)-\frac{5}{3}:\frac{1}{9}\)
\(\frac{2,3}{7}-\frac{76}{63}-15\)
\(-\frac{55,3}{63}-15\)
\(-15\frac{55,3}{63}\)
- \(\dfrac{1}{9}\) \(\times\) ( - \(\dfrac{3}{5}\)) + \(\dfrac{5}{-6}\) \(\times\) ( \(-\dfrac{3}{5}\)) - \(\dfrac{7}{2}\) \(\times\) \(\dfrac{3}{5}\)
= \(\dfrac{1}{9}\) \(\times\) \(\dfrac{3}{5}\) + \(\dfrac{5}{6}\) \(\times\) \(\dfrac{3}{5}\) - \(\dfrac{7}{2}\) \(\times\) \(\dfrac{3}{5}\)
= \(\dfrac{3}{5}\) \(\times\) ( \(\dfrac{1}{9}\) + \(\dfrac{5}{6}\) - \(\dfrac{7}{2}\))
= \(\dfrac{3}{5}\) \(\times\) ( \(\dfrac{2}{18}\) + \(\dfrac{15}{18}\) - \(\dfrac{63}{18}\))
= \(\dfrac{3}{5}\) \(\times\) (- \(\dfrac{23}{9}\))
= - \(\dfrac{23}{15}\)