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SD
1
25 tháng 11 2018
\(\dfrac{\left(-5\right)^2.20^2}{8^2.125}=\dfrac{\left[\left(-5\right).20\right]^2}{2^{3^2}.5^3}=\dfrac{\left(-100\right)^2}{\text{4^3}.5^3}=\dfrac{10000}{\left(4.5\right)^3}=\dfrac{10000}{20^3}\dfrac{10000}{8000}=\dfrac{5}{4}\)
10 tháng 11 2018
a. \(\frac{\left(-5\right)^2.20^4}{8^2.\left(-125\right)}=\frac{\left(-5\right)^2.5^4.2^8}{2^6.\left(-5\right)^3}=\left(-5\right)^3.2^2=\left(-125\right).4=-500\)
b, \(\frac{15^{11}.5^7.9^2}{5^{18}.27^6}=\frac{3^{11}.5^{11}.5^7.3^4}{5^{18}.3^{18}}=\frac{3^{15}.5^{18}}{5^{18}.3^{18}}=\frac{1}{3^3}=\frac{1}{27}\)
PT
1
1
2
HN
2
31 tháng 7 2018
\(\left(\frac{2}{3}-\frac{4}{7}\right):\frac{5}{9}+\left(-\frac{8}{7}+\frac{1}{3}\right):\frac{5}{9}\)
\(=\left[\left(\frac{2}{3}-\frac{4}{7}\right)+\left(-\frac{8}{7}+\frac{1}{3}\right)\right]:\frac{5}{9}\)
\(=\left(\frac{2}{3}-\frac{4}{7}-\frac{8}{7}+\frac{1}{3}\right)\cdot\frac{9}{5}\)
\(=\left(1-\frac{12}{7}\right)\cdot\frac{9}{5}\)
\(=-\frac{5}{7}\cdot\frac{9}{5}\)
\(-\frac{9}{7}\)
31 tháng 7 2018
\(\left(\frac{2}{3}-\frac{4}{7}\right):\frac{5}{9}+\left(-\frac{8}{7}+\frac{1}{3}\right):\frac{5}{9}\)
\(=\left(\frac{14}{21}-\frac{12}{21}\right):\frac{5}{9}+\left(-\frac{24}{21}+\frac{7}{21}\right):\frac{5}{9}\)
\(=\frac{2}{21}:\frac{5}{9}+\frac{-17}{21}:\frac{5}{9}\)
\(=\left(\frac{2}{21}+\frac{-17}{21}\right):\frac{5}{9}\)
\(=\frac{-15}{21}:\frac{5}{9}\)
\(=\frac{-15}{21}.\frac{9}{5}\)
\(=\frac{-9}{7}\)
\(=\frac{99}{35}\)
HA
1
14 tháng 12 2018
Mình ko ghi lại đề nha
=>(-1/5)2x5-(26x38/37x26)
=1/5-3
=-14/5
19 tháng 4 2017
Thực hiện các phép tính:
a) 9,6.212−(2.125−1512):149,6.212−(2.125−1512):14
b) 518−1,456:725+4,5.45518−1,456:725+4,5.45;
c) (12+0,8−113).(2,3+4725−1,28)(12+0,8−113).(2,3+4725−1,28)
d) (−5).12:[(−14)+12:(−2)]+113(−5).12:[(−14)+12:(−2)]+113.
Hướng dẫn làm bài:
a) 9,6.212−(2.125−1512):149,6.212−(2.125−1512):14
=9,6.52−(250−1712)×4=9,6.52−(250−1712)×4
=4,8.5−(1000−173)=4,8.5−(1000−173)
=24−1000+173=24−1000+173
=−976+173=−976+173
=−97013=−97013
b) 518−1,456:725+4,5.45518−1,456:725+4,5.45;
=518−1,456×257+92.45=518−1,456×257+92.45
=518−0,208×25+185=518−0,208×25+185
=518−5,2+185=518−5,2+185
=25−468+32490=25−468+32490
=−11990=−11990
c) (12+0,8−113).(2,3+4725−1,28)(12+0,8−113).(2,3+4725−1,28)
=(12+45−43).(2310+10725−3225)=(12+45−43).(2310+10725−3225)
=(15+24−4030).(2310+10725−3225)=(15+24−4030).(2310+10725−3225)
=(15+24−4030).(115+214−6450)=(15+24−4030).(115+214−6450)
=−130.26550=−130.26550
=−53300=−53300
d) (−5).12:[(−14)+12:(−2)]+113(−5).12:[(−14)+12:(−2)]+113
=−60:[14+12×(−12)]+1.13=−60:[14+12×(−12)]+1.13
=−60:[−14−14]+113=−60:[−14−14]+113
=−60:(12)+113=−60:(12)+113
=120+113=120+113
=12113
LH
19 tháng 4 2017
a) \(9,6.2\dfrac{1}{2}-\left(2.125-1\dfrac{5}{12}\right):\dfrac{1}{4}\)
\(=9,6.\dfrac{5}{2}-\left(250-\dfrac{17}{12}\right).4\)
\(=4,8.5-\left(1000-\dfrac{17}{3}\right)\)
\(=24-1000+\dfrac{17}{3}\)
\(=-976+\dfrac{17}{3}=-970\dfrac{1}{3}\)
b) \(\dfrac{5}{18}-1,456:\dfrac{7}{25}+4,5.\dfrac{4}{5}\)
\(=\dfrac{5}{18}-1,456.\dfrac{25}{7}+\dfrac{9}{2}.\dfrac{4}{5}\)
\(=\dfrac{5}{18}-0,208.25+\dfrac{18}{5}\)
\(=\dfrac{5}{18}-5,2+\dfrac{18}{5}\)
\(=-\dfrac{119}{90}\)
c) \(\left(\dfrac{1}{2}+0,8-1\dfrac{1}{3}\right).\left(2,3+4\dfrac{7}{25}-1,28\right)\)
\(=\left(\dfrac{1}{2}+\dfrac{4}{5}-\dfrac{4}{3}\right).\left(\dfrac{23}{10}+\dfrac{107}{25}-\dfrac{32}{25}\right)\)
\(=-\dfrac{1}{30}.\dfrac{265}{50}=-\dfrac{53}{300}\)
d) \(\left(-5\right).12:\left[\left(-\dfrac{1}{4}\right)+\dfrac{1}{2}:\left(-2\right)\right]+1\dfrac{1}{3}\)
\(=-60:\left[\dfrac{1}{4}+\dfrac{1}{2}.\dfrac{-1}{2}\right]+1.\dfrac{1}{3}\)
\(=-60:\left[-\dfrac{1}{4}-\dfrac{1}{4}\right]+1\dfrac{1}{3}\)
\(=-60:\left(\dfrac{1}{2}\right)+1\dfrac{1}{3}\)
\(=121\dfrac{1}{3}\)
28 tháng 10 2016
Đặt A=\(\frac{11}{5^2\cdot6^2}+\frac{13}{6^2\cdot7^2}+\frac{15}{7^2\cdot8^2}+...+\frac{39}{19^2\cdot20^2}\)
A=\(\frac{11}{25\cdot36}+\frac{13}{36\cdot49}+\frac{15}{49\cdot64}+...+\frac{39}{361\cdot400}\)
A=\(\frac{1}{25}-\frac{1}{36}+\frac{1}{36}-\frac{1}{49}+\frac{1}{49}-\frac{1}{64}+...+\frac{1}{361}-\frac{1}{400}\)
A=\(\frac{1}{25}-\frac{1}{400}\)
A=\(\frac{3}{80}\)
\(\Rightarrow\)A không phải là số nguyên
28 tháng 10 2016
\(\frac{11}{5^2.6^2}+\frac{13}{6^2.7^2}+\frac{15}{7^2.8^2}+...+\frac{39}{19^2.20^2}\)
\(=\frac{11}{25.36}+\frac{13}{36.49}+\frac{15}{49.64}+...+\frac{39}{361.400}\)
\(=\frac{1}{25}-\frac{1}{36}+\frac{1}{36}-\frac{1}{49}+\frac{1}{49}-\frac{1}{64}+...+\frac{1}{361}-\frac{1}{400}\)
\(=\frac{1}{25}-\frac{1}{400}\)
\(=\frac{3}{80}\)
Mà \(\frac{3}{80}\notin Z\)
\(\Rightarrow\frac{11}{5^2+6^2}+\frac{13}{6^2.7^2}+\frac{15}{7^2.8^2}+...+\frac{39}{19^2.20^2}\notin Z\)
\(\frac{\left(-5\right)^2.20^4}{8^2.125}=\frac{25.20^4}{8^2.25.5}=\frac{20^4}{8^2.5}=500\)