(\(\frac{2121}{1212}\) + \(\frac{2121}{2020}\) + \(\frac{2121}{3030}\) + \(\frac{2121}{4242}\) ) - x = - 2015 tính đi
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4 tháng 5 2019
\(\left(\frac{2121}{1212}+\frac{2121}{2020}+\frac{2121}{3030}+\frac{2121}{4242}\right)-x=-2015\)
\(\left(\frac{21}{12}+\frac{21}{20}+\frac{21}{30}+\frac{1}{2}\right)=-2015+x\)
\(\left(\frac{7}{3}+\frac{21}{20}+\frac{7}{10}+\frac{1}{2}\right)=-2015+x\)
\(\left(\frac{140}{60}+\frac{63}{60}+\frac{42}{60}+\frac{30}{60}\right)=-2015+x\)
\(\frac{275}{60}=-2015+x\)
\(\frac{55}{12}+2015=x\)
\(x=\frac{55}{12}+\frac{24180}{12}\)
\(x=\frac{24235}{12}\)
DN
3
LT
2
13 tháng 3 2020
1212+2121+4242+2424
=1212+2121+2121+2121+1212+1212
=(1212+2121)+(2121+1212)+(1212+2121)
=3333+3333+3333
=3333 x 3 =9999
23 tháng 5 2018
\(\frac{242}{363}+\frac{1616}{2121}=\frac{2}{7}.\frac{2015}{A}\)
\(\frac{11.11.2}{11.11.3}+\frac{101.16}{101.21}=\frac{2}{7}.\frac{2015}{A}\)
\(\frac{2}{3}+\frac{16}{21}=\frac{2}{7}.\frac{2015}{A}\)
\(\Rightarrow\frac{2}{7}.\frac{2015}{A}=\frac{10}{7}\)
\(\frac{2015}{A}=\frac{10}{7}:\frac{2}{7}\)
\(\frac{2015}{A}=5\)
\(A=2015:5\)
\(A=403\)
23 tháng 5 2018
\(\left(\frac{242}{363}+\frac{1616}{2121}\right)=\frac{2}{7}.\frac{2015}{A}\)
\(\Leftrightarrow\left(\frac{2}{3}+\frac{16}{21}\right)=\frac{2}{7}.\frac{2015}{A}\)
\(\Leftrightarrow\frac{10}{7}=\frac{2}{7}.\frac{2015}{A}\)
\(\Leftrightarrow5=\frac{2015}{A}\)
\(\Leftrightarrow A=403\)
TM
6
14 tháng 8 2018
18 x \(\left(\frac{1919}{2121}+\frac{888}{999}\right)\)
= 18 x \(\frac{113}{63}\)
= \(\frac{226}{7}\)
PN
1
1 tháng 6 2018
\(\frac{1414+1515+1616+1717+1818+1919}{2020+2121+2222+2323+2424+2525}\)
\(=\frac{101\times\left(14+15+16+17+18+19\right)}{101\times\left(20+21+22+23+24+25\right)}\)
\(=\frac{14+15+16+17+18+19}{20+21+22+23+24+25}\)
+) Tử số :
Số các số hạng là : ( 19 - 14 ) : 1 + 1 = 6 ( số )
Tổng là : ( 19 + 14 ) x 6 : 2 = 99
+) Mẫu số :
Số các số hạng là : ( 25 - 20 ) : 1 + 1 = 6 ( số )
Tổng là : ( 25 + 20 ) x 6 : 2 = 135
\(\Leftrightarrow\frac{99}{135}=\frac{11}{15}\)
DG
1
20 tháng 8 2017
\(\frac{1414+1515+1616+1717+1818+1919}{2020+2121+2222+2323+2424+2525}\)
\(=\frac{101\left(14+15+16+17+18+19\right)}{101\left(20+21+22+23+24+25\right)}\)
\(=\frac{\left(19+14\right)\left(19-14+1\right):2}{\left(25+20\right)\left(25-20+1\right):2}\)
=\(\frac{33.6:2}{45.6:2}=\frac{33}{45}=\frac{11}{15}\)
16 tháng 9 2017
\(\frac{1010+1111+1212+1313+1414+1515+1616+1717}{2020+2121+2222+2323+2424+2525+2626+2727}\)
\(=\frac{101.10+101.11+...+101.17}{101.20+101.21+...+101.27}\)
\(=\frac{101.\left(10+11+...+17\right)}{101.\left(20+21+...+27\right)}\)
\(=\frac{108}{188}\)
\(=\frac{27}{47}\)
16 tháng 9 2017
\(2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{4}{96}\right)\cdot5.y>\frac{5}{6}\)
\(\Rightarrow2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{1}{24}\right):5.y>\frac{5}{6}\)
\(\Rightarrow2>\left(\frac{20}{120}+\frac{16}{120}+\frac{9}{120}+\frac{5}{120}\right):5.y>\frac{5}{6}\)
\(\Rightarrow2>\frac{5}{12}:5.y>\frac{5}{6}\)
\(\Rightarrow2>\frac{1}{12}.y>\frac{5}{6}\)
Đặt :\(\frac{1}{12}.y=2\Rightarrow y=2:\frac{1}{12}=24\)
\(\frac{1}{12}.y=\frac{5}{6}\Rightarrow y=\frac{5}{6}:\frac{1}{12}=10\)
\(\Rightarrow24>y>10\)
\(\Rightarrow y\in\left\{11;12;...;23\right\}\)
=>(\(\frac{7}{4}+\frac{21}{20}+\frac{7}{10}+\frac{1}{2}\))-x=-2015
=>(1,75+1,05+0,7+0,5)-x=-2015
=>4-x=-2015
=>x=4-(-2015)
=>x=2019
(\(\frac{2121}{1212}+\frac{2121}{2020}+\frac{2121}{3030}+\frac{2121}{4242}\)) - x = -2015
=> ( \(\frac{21}{12}+\frac{21}{20}+\frac{21}{30}+\frac{21}{42}\) ) - x = -2015
=> ( \(\frac{7}{4}+\frac{21}{20}+\frac{21}{30}+\frac{1}{2}\) ) - x = -2015
=> ( 1,75 + 1,05 + 0,7 + 0,5 ) - x = -2015
=> 4 - x = -2015
=> x = 4 - ( -2015 )
=> x = 4 + 2015
=> x = 2019