Tính
\(\frac{5}{13}+-\frac{5}{17}+-\frac{20}{41}+\frac{8}{13}+-\frac{21}{41}\)
K
Khách
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N
18 tháng 8 2017
\(A=\frac{5}{13}+\frac{-5}{7}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(A=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(-\frac{20}{41}+\frac{-21}{41}\right)+\left(-\frac{5}{7}\right)\)
\(A=1+\left(-1\right)-\frac{5}{7}\)
\(A=0+\left(-\frac{5}{7}\right)\)
\(A=-\frac{5}{7}\)
18 tháng 8 2017
A=5/13-5/7-20/41+8/13-21/41
A=5/13+8/13-20/41-21/41-5/7
A=13/13-41/41-5/7
A=1-1-5/7
A=0-5/7
A=-5/7
Vậy A=-5/7
tk nha bn
26 tháng 7 2016
p) \(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\)
\(=\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)
\(=-1+1+\frac{-2}{11}\)
\(=-\frac{2}{11}\)
q) \(\frac{5}{13}+\frac{-5}{17}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{17}\)
\(=1+\left(-1\right)+\frac{-5}{17}=\frac{-5}{17}\)
r) \(\frac{1}{5}+\frac{-2}{9}+\frac{-7}{9}+\frac{4}{5}+\frac{16}{17}\)
\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+\frac{-7}{9}\right)+\frac{16}{17}\)
\(=1+\left(-1\right)+\frac{16}{17}=\frac{16}{17}\)
21 tháng 6 2015
a,\(=\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{-4}{9}+\frac{7}{15}\)
\(\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)
=-1+1+-2/11
=0+-2/11
=-2/11
b,\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{40}\right)+\frac{-5}{17}\)
=1+-1+-5/17
=0+-5/17
=-5/17
c,\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+-\frac{7}{9}\right)+\frac{16}{17}\)
=1+-1+16/17
=0+16/17
=16/17
d,\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\)
\(=\frac{1}{3}-\frac{1}{101}=\frac{98}{303}\)
21 tháng 6 2015
a.\(\frac{-5}{9}\)+\(\frac{8}{15}\)+\(\frac{-2}{11}\)+\(\frac{4}{-9}\)+\(\frac{7}{15}\)
=\(\frac{-5}{9}\)+\(\frac{4}{-9}\)+\(\frac{8}{15}\)+\(\frac{7}{15}\)+\(\frac{-2}{11}\)
=(\(\frac{-5}{9}\)+\(\frac{-4}{9}\))+(\(\frac{8}{15}\)+\(\frac{7}{15}\))+\(\frac{-2}{11}\)
=(-1)+1+\(\frac{-2}{11}\)
=0+\(\frac{-2}{11}\)
=\(\frac{-2}{11}\).
ON
11 tháng 2 2018
Mình không ghi lại đầu bài nhé bạn
=\(\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{7}\)
=\(1+\left(-1\right)+\frac{-5}{7}\)
=\(\frac{-5}{7}\)
11 tháng 2 2018
\(\frac{5}{13}+\frac{-5}{7}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{7}\)
\(=1+\left(-1\right)+\frac{-5}{7}\)
\(=0+\frac{-5}{7}\)
\(=\frac{-5}{7}\)
CHÚC BN HỌC TỐT!!!!
18 tháng 4 2015
RÚT GỌN:
\(\frac{3.13-13.18}{15.40-80}=\frac{13.\left(3-18\right)}{15.40-40.2}=\frac{13.\left(-15\right)}{40\left(15-2\right)}=\frac{13.\left(-15\right)}{40.13}=-\frac{15}{40}=-\frac{3}{8}\)
CHỨNG MINH:
Ta thấy \(\frac{1}{101}>\frac{1}{150};\frac{1}{102}>\frac{1}{150};...;\frac{1}{149}>\frac{1}{150}\)
=>\(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{150}>\frac{1}{150}.\left(150-101+1\right)=\frac{1}{150}.50=\frac{50}{150}=\frac{1}{3}\)(đpcm)
TÍNH HỢP LÝ:
B=\(\frac{5}{13}+\frac{-5}{7}-\frac{20}{41}+\frac{8}{13}+\frac{-21}{41}=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-21}{41}-\frac{20}{41}\right)+\frac{-5}{7}=1+\left(-1\right)+\frac{-5}{7}=0+\frac{-5}{7}=\frac{-5}{7}\)
24 tháng 4 2018
a)=3/4 -3/2+1/2 *12/5=3/4 -3/2 +6/5=30/40 -60/40 +48/40=9/20 b)75/287 c)1
QA
17 tháng 12 2019
Thực hiện phép tính ( bằng cách hợp lí nếu có thể):
a, \(5\frac{4}{13}.15\frac{3}{41}-5\frac{4}{13}.2\frac{3}{41}\)
\(=5\frac{4}{13}\left(15\frac{3}{41}-2\frac{3}{41}\right)\)
\(=15\frac{4}{13}\left(\frac{618}{41}-\frac{85}{41}\right)\)
\(=\frac{69}{13}.13\)
\(=69\)
b, \(6.\left(-\frac{1}{3}\right)^2-\left(\frac{1}{4}:2-\frac{7}{16}.\frac{-4}{21}\right)\)
\(=6.\frac{1}{9}-\left(\frac{1}{8}-\frac{-1}{12}\right)\)
\(=\frac{2}{3}-\left(\frac{3}{24}-\frac{-2}{24}\right)\)
\(=\frac{2}{3}-\frac{5}{24}\)
\(=\frac{16}{24}-\frac{5}{24}\)
\(=\frac{11}{24}\)
Chúc bạn hok tốt!!! lưu khánh huyền
\(\frac{5}{13}+-\frac{5}{17}+-\frac{20}{41}+\frac{8}{13}+-\frac{21}{41}\)
\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(-\frac{20}{41}+-\frac{21}{41}\right)+-\frac{5}{17}\)
\(=1+\left(-1\right)+-\frac{5}{17}\)
\(=0+-\frac{5}{17}\)\(=-\frac{5}{17}\)
Ủng hộ tk Đúng nhé mọi người !!! ^^