= ( 5/7 + -15/7 ) . ( -4/19 + 5/19 )
=10/7 . 1/19
=10/133
=5/7.-4/19+5/7.-3.5/19
=5/7.{-4/19+-3.5/19}
=5/7.-1
-5/7
Thực hiện phép tính ( tính nhanh nếu có thể)
a)3\(\dfrac{14}{19}\) +\(\dfrac{13}{17}\)+\(\dfrac{35}{43}\)+ 6\(\dfrac{5}{19}\) + \(\dfrac{8}{43}\)
b) \(\dfrac{-5}{7}\) . \(\dfrac{2}{11}\) + \(\dfrac{-5}{7}\) . \(\dfrac{9}{11}\) + 1\(\dfrac{5}{7}\)
c) 11\(\dfrac{3}{13}\) - ( 2\(\dfrac{4}{7}\) + 5\(\dfrac{3}{13}\))
d) \(\dfrac{2}{7}\) . 5\(\dfrac{1}{4}\) - \(\dfrac{2}{7}\) . 3\(\dfrac{1}{4}\)
Tính bằng cách hợp lý
a)\(\dfrac{7}{15}\)-(\(\dfrac{2}{15}\)-\(\dfrac{12}{18}\))
b) (\(\dfrac{7}{41}\)-\(\dfrac{4}{9}\))-(\(\dfrac{3}{19}\)+\(\dfrac{7}{41}\))+(\(\dfrac{4}{9}\)-\(\dfrac{16}{19}\))
1.Tính nhanh:
A= \(\dfrac{\dfrac{2}{3}-\dfrac{1}{4}+\dfrac{5}{11}}{\dfrac{5}{12}+1-\dfrac{7}{11}}\)
2. Cho: B =\(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{6}+...+\dfrac{1}{19}\) .Hãy chứng tỏ rằng B > 1.
3. Rút gọn:
a) C= \(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{4}\right)....\left(1-\dfrac{1}{20}\right)\)
b) D= \(1+\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2012}}\)
4. So sánh: E=\(\dfrac{20^{10}+1}{20^{10}-1}\) và F =\(\dfrac{20^{10}-1}{20^{10}-3}\)
5. Tính giá trị của biểu thức:
M= \(\dfrac{\dfrac{3}{5}+\dfrac{3}{7}-\dfrac{3}{11}}{\dfrac{4}{5}+\dfrac{4}{7}-\dfrac{4}{11}}\)
tính nhanh
\(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
Bài 1. Thực hiện phép tính:
a) |5.0,6+\(\dfrac{2}{3}\)|- \(\dfrac{1}{3}\)
b)(0,25 - 1\(\dfrac{1}{4}\)) : 5 - \(\dfrac{1}{5}\).(-3)\(^2\)
c)\(\dfrac{14}{17}.\dfrac{7}{5}-\dfrac{-3}{17}:\dfrac{5}{7}\)
d)\(\dfrac{7}{16}+\dfrac{-9}{25}+\dfrac{9}{16}+\dfrac{-16}{25}\)
e)\(\dfrac{5}{6}+2\sqrt{\dfrac{4}{9}}\)
tính
a) \(\dfrac{1}{5}:\dfrac{-7}{15}-\dfrac{-2}{7}\)
b) \(\dfrac{5}{6}-\dfrac{2}{3}+\dfrac{1}{4}\)
Thực hiện phép tính:
a) \(1\dfrac{13}{15}\). (-5)2. 3 + (\(\dfrac{8}{15}-\dfrac{19}{60}\)) : \(1\dfrac{23}{24}\)
b) \(\dfrac{\left(\dfrac{11^2}{200}+0.414:0.01\right)}{\dfrac{1}{12}-37.25+3\dfrac{1}{6}}\)
nhanh nhé mik cần gấp!
\(M=1\dfrac{1}{10}\dfrac{15}{19}-\dfrac{22}{38}\cdot0,5+110\%\cdot\dfrac{9}{19}\)
tính
\(\dfrac{-5}{7}.\dfrac{5}{11}+\dfrac{-5}{7}.\dfrac{2}{11}-\dfrac{5}{7}:\dfrac{11}{4}\)