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= 1/2 - 1/4 + 1/4 - 1/6 + 1/6 - 1/8 +......+ 1/2014 - 1/2016
= 1/2 - 1/2016
= 1008/2016 - 1/2016
= 1007/2016
không chắc lắm!!!
\(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{2014.2016}\)
=\(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2014}-\frac{1}{2016}\)
<=>\(\frac{1}{2}-\left(-\frac{1}{2016}\right)=\frac{1}{2}+\frac{1}{2016}=\frac{1009}{2016}\)
\(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+....+\frac{2}{2014.2016}\)
\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2014}-\frac{1}{2016}\)
\(=\frac{1}{2}-\frac{1}{2016}=\frac{1008}{2016}-\frac{1}{2016}=\frac{1007}{2016}\)
Câu 1 :
\(\frac{1}{5}:\frac{3}{6}=\frac{1}{5}\times\frac{6}{3}\)
\(=\frac{6}{15}=\frac{2}{5}\)
Câu 2 :
\(\frac{4}{8}+\frac{2}{4}=\frac{1}{2}+\frac{1}{2}\)
\(=1\)
Câu 3 :
\(\frac{2}{5}\times\frac{6}{4}=\frac{12}{20}=\frac{6}{10}\)
Câu 4 :
\(\frac{7}{6}-\frac{2}{3}=\frac{7}{6}-\frac{4}{6}\)
\(=\frac{3}{6}=\frac{1}{2}\)
\(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+....+\frac{2}{2014.2016}\)
\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+......+\frac{1}{2014}-\frac{1}{2016}\)
\(=\frac{1}{2}-\frac{1}{2016}\)
\(=\frac{1008}{2016}-\frac{1}{2016}=\frac{1007}{2016}\)
\(\frac{2}{2\times4}+\frac{2}{4\times6}+...+\frac{2}{2014\times2016}\)
=\(\left(\frac{2}{2}-\frac{2}{4}\right)+\left(\frac{2}{4}-\frac{2}{6}\right)+...+\left(\frac{2}{2014}-\frac{2}{2016}\right)\)
=\(\frac{2}{2}-\frac{2}{4}+\frac{2}{4}-\frac{2}{6}+...+\frac{2}{2014}-\frac{2}{2016}\)
=\(\frac{2}{2}-\frac{2}{2016}=\frac{1007}{1008}\)
1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9=135
5/6 bạn nha
5/6 HT