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1/3xD=1/(2x4)+1/(4x6)+...+1/(98x100)
2/3xD=2/(2x4)+2/(4x6)+...+1/(98x100)
2/3xD= 1/2-1/4+1/4-1/6+...+1/98-1/100
2/3xD=1/2-1/100
2/3xD=49/100
D=147/200
Nguyễn Hiền Anh!
Đặt phân thức trên là D
=> D=(1+1+1+1+...+1+2013/2+2012/3+...+2/2013+1/2014)/(1/2+1/3+1/4+...+1/2014)
=> D=(1+2013/2+1+2012/3+1+2011/4+...+1+2/2013+1+1/2014+1)/(1/2+1/3+1/4+1/5+...+1/2014)
=> D=(2015/2+2015/3+2015/4+...+2015/2013+2015/2014+1)/(1/2+1/3+1/4+...+1/2014)
=> D=[2015*(1/2+1/3+1/4+1/5+....+1/2014)]/(1/2+1/3+1/4+1/5+...+1/2014)
=> D=2015
a) MC :24
\(\frac{1}{3}+\frac{3}{8}-\frac{7}{12}=\frac{1\times8+3\times3-7\times2}{24}=\frac{3}{24}=\frac{1}{8}\)
b)MC : 56
\(\frac{3}{14}+\frac{5}{8}-\frac{1}{2}=\frac{3\times4+5\times7-1\times28}{56}=\frac{19}{56}\)
c) MC: 36
\(\frac{1}{4}-\frac{2}{3}-\frac{11}{18}=\frac{1\times9-2\times12-11\times2}{36}=\frac{-37}{36}\)
d) MC: 312
\(\frac{1}{4}+\frac{5}{12}-\frac{1}{13}-\frac{7}{8}=\frac{1\times78+5\times26-1\times24-7\times39}{312}=\frac{-89}{312}\)
= 14 : ( 14/3 - 14/9 ) + 14 : ( 2/3 + 8/9 )
= 14 : 28/9 + 14 : 14/9
= 14 * 9/28 + 14 * 9/14
= 14 * ( 9/28 + 9/14 )
= 14 * 27/28
= 27/2
Ta có:
A=\(14:\left(\frac{14}{3}-\frac{14}{5}\right)+14:\left(\frac{2}{3}+\frac{8}{9}\right)\)
\(=14:\left(\frac{14}{3}-\frac{14}{5}+\frac{2}{3}+\frac{8}{9}\right)\)
\(=14:\left(\frac{42+6+8}{3}-\frac{14}{5}\right)\)
\(=14:\left(\frac{56}{3}-\frac{14}{5}\right)\)
\(=14:\left(\frac{280-42}{15}\right)=14:\left(\frac{238}{15}\right)=14\cdot\frac{15}{238}=\frac{210}{238}\)
ko biết có tính sai chỗ nào ko
\(=\frac{19}{4}+\left(-0.37\right)+\frac{1}{8}+\left(-1.28\right)+\left(-2.5\right)+\frac{37}{12}\)\(\frac{37}{12}\)
\(=\left(\frac{19}{4}+\frac{1}{8}+\frac{37}{12}\right)+\left(\left(-0.37\right)+\left(-1.28\right)+\left(-2.5\right)\right)\)
\(=\frac{191}{24}+\left(-\frac{83}{20}\right)\)
\(=\frac{457}{120}\)
tu giai di ko biet nha!!!!