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GR
2
13 tháng 1 2017
ta có : 144.x=56+130.x
144.x-130.x=56
(144-130).x=56
14.x=56suy ra x=4
19 tháng 7 2015
a,b you cứ tính bt nhé
c)\(\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)
\(=\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}\)
\(=\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\)
\(=\frac{1}{4}-\frac{1}{11}\)
\(=\frac{7}{44}\)
d) \(\frac{5^2}{1.6}+\frac{5^2}{6.11}+\frac{5^2}{11.16}+\frac{5^2}{16.21}+\frac{5^2}{21.26}+\frac{5^2}{26.31}\)
\(=5\left(\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+\frac{5}{26.31}\right)\)
\(=5\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+\frac{1}{26}-\frac{1}{31}\right)\)
\(=5\left(1-\frac{1}{31}\right)\)
\(=5.\frac{30}{31}\)
\(=\frac{150}{31}\)
S
22 tháng 4 2018
\(\frac{1}{3}+\frac{1}{6}+...+\frac{2}{x\left(x+1\right)}=\frac{2003}{2009}\)
\(\Rightarrow\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right)}=\frac{2003}{2009}\)
\(\Rightarrow2\left(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{x\left(x+1\right)}\right)=\frac{2003}{2009}\)
\(\Rightarrow2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2003}{2009}\)
\(\Rightarrow2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2003}{2009}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{2003}{2009}\div2\)
\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{2003}{4018}\)
\(\Rightarrow\frac{1}{x+1}=\frac{1}{2}-\frac{2003}{4018}\)
\(\Rightarrow\frac{1}{x+1}=\frac{3}{2009}\)
\(\Rightarrow\frac{3}{3\left(x+1\right)}=\frac{3}{2009}\)
\(\Rightarrow3\left(x+1\right)=2009\)
\(\Rightarrow3x+3=2009\)
\(\Rightarrow3x=2006\)
\(\Rightarrow x=\frac{2006}{3}\)
MT
12 tháng 7 2015
\(a,\frac{\left(21\right)^{15}.49^{11}.5^6}{\left(63\right)^{14}.7}=\frac{\left(3.7\right)^{15}.\left(7^2\right)^{11}.5^6}{\left(3^2.7\right)^{14}.7}=\frac{3^{15}.7^{15}.7^{22}.5^6}{\left(3^2\right)^{14}.7^{14}}=\frac{3^{15}.7^{37}.5^6}{3^{28}.7^{14}}\)
\(=\frac{7^{23}.5^6}{3^{13}}\)
sao số to thế nhỉ
TL
0
\(\left(-12\right)^2.x=56+10.13.10\)
\(\left(-12\right)^2.x=56+1300\)
\(\left(-12\right)^2.x=1356\)
\(-12.-12.x=1356\)
\(144.x=1356\)
\(x=1356:144\)
\(x=9,4166666666...\)
(-12)^2.x=56+10.13.10
144.x=56+1300
144.x=1356
x=1356:144
x=10