-5/7.4/13+-5/7.9/13+-2/7
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29 tháng 3 2016
=-3/7.(4/13+9/13)+3/7
=-3/7.13/13+3/7
=-3/7.1+3/7
=-3/7+3/7
=0
3 tháng 4 2019
2\3x-780\11:[13\2.(1\3.5+1\5.7+1\7.9+1\9.11]=-5
2\3x-780\11:[13\2.(1\3-1\5+1\5-1\7+....+1\9-1\11)]=-5
2\3x-780\11:[13\2.(1\3-1\11)]=-5
2\3x-780\11:[13\2.8\33]=-5
2\3x-780\11:52\33=-5
2\3x-525\13=-5
2\3x=-5+525\13
2\3x=460\13
x=460\13:2\3
x=690\13
PA
6 tháng 7 2016
\(A=\frac{7\times9+14\times27+21\times36}{21\times27+42\times81+63\times108}=\frac{7\times9+7\times2\times9\times3+7\times3\times9\times4}{21\times27+21\times2\times27\times3+21\times3\times27\times4}=\frac{7\times9\times\left(1+2\times3+3\times4\right)}{21\times27\times\left(1+2\times3\times3\times4\right)}=\frac{7\times3\times3}{7\times3\times3\times9}=\frac{1}{9}\)
NT
2
14 tháng 7 2021
a) Ta có: \(\dfrac{3}{5\cdot7}+\dfrac{3}{7\cdot9}+...+\dfrac{3}{59\cdot61}\)
\(=\dfrac{3}{2}\left(\dfrac{2}{5\cdot7}+\dfrac{2}{7\cdot9}+...+\dfrac{2}{59\cdot61}\right)\)
\(=\dfrac{3}{2}\left(\dfrac{1}{5}-\dfrac{1}{61}\right)\)
\(=\dfrac{3}{2}\cdot\dfrac{56}{305}=\dfrac{84}{305}\)
VH
0
1 tháng 10 2021
\(a,=\dfrac{3}{2}-\dfrac{5}{6}:\dfrac{1}{4}+\sqrt{\dfrac{1}{4}-\dfrac{1}{2}}=\dfrac{3}{2}-\dfrac{10}{3}+\sqrt{\dfrac{1}{2}}=-\dfrac{11}{6}+\dfrac{\sqrt{2}}{2}=\dfrac{-33+3\sqrt{2}}{6}\)
\(b,=-\dfrac{4}{3}\cdot\dfrac{9}{2}+\dfrac{13}{12}\cdot\left(-\dfrac{8}{13}\right)=6-\dfrac{2}{3}=\dfrac{16}{3}\\ c,=\dfrac{1}{4}-\left(-\dfrac{1}{6}:4-8\cdot\dfrac{1}{16}\right)=\dfrac{1}{4}-\left(-\dfrac{1}{24}-\dfrac{1}{2}\right)\\ =\dfrac{1}{4}-\dfrac{13}{24}=-\dfrac{7}{24}\\ d,=\dfrac{3^{11}\cdot5^{11}\cdot5^7\cdot3^4}{5^{18}\cdot3^{18}}=\dfrac{1}{3^3}=\dfrac{1}{27}\)
TH
1
3 tháng 8 2020
a) \(-1\frac{1}{15}:2\frac{1}{2}=-\frac{16}{15}:\frac{5}{2}=-\frac{16}{15}\cdot\frac{2}{5}=-\frac{32}{75}\)
b) \(\frac{1}{3}-\frac{5}{14}\cdot\frac{21}{25}=\frac{1}{3}-\frac{1}{2}\cdot\frac{3}{5}=\frac{1}{3}-\frac{3}{10}=\frac{1}{30}\)
c) \(\frac{-5}{7}\cdot\frac{2}{11}+\frac{-5}{7}\cdot\frac{9}{11}+1\frac{5}{7}\)
\(=-\frac{5}{7}\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{12}{7}\)
\(=-\frac{5}{7}\cdot1+\frac{12}{7}=-\frac{5}{7}+\frac{12}{7}=\frac{7}{7}=1\)
d) \(8\frac{1}{4}-\left(2\frac{5}{9}+3\frac{1}{4}\right)=8\frac{1}{4}-2\frac{5}{9}-3\frac{1}{4}=\left(8\frac{1}{4}-3\frac{1}{4}\right)-2\frac{5}{9}\)
\(=5-2\frac{5}{9}=5-\frac{23}{9}=\frac{22}{9}\)
e) \(\frac{1}{4}\cdot\frac{12}{13}+\frac{1}{4}\cdot\frac{1}{13}-25=\frac{1}{4}\left(\frac{12}{13}+\frac{1}{13}\right)-25=\frac{1}{4}\cdot1-25=\frac{1}{4}-25=-\frac{99}{4}\)
=-0.38637482941