Câu hỏi của Mun - Toán lớp 5 - Học toán với OnlineMath

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A = 2011.2010−12009.2011+2010 

 => \(\frac{2011.2009+2011-1}{2009.2011+2010}\) = \(\frac{2011.2009+2010}{2009.2011+2010}=1\) 

=> A = 1

t i c k nhé!! 354543564576856925253456456545756756887676976

\(A=\frac{2011.2010-1}{2009.2011+2010}\)

\(A=1\)

nha bạn                                      ^_^

\(\dfrac{2011x2010-1}{2009x2011+2010}\)

=\(\dfrac{2011x\left(2009+1\right)-1}{2009x2011+2010}\)

\(=\dfrac{2011x2009+2011-1}{2011x2009+2010}\)

=\(\dfrac{2011x2009+2010}{2011x2009+2010}\)

=

Học tốt :>

ôi bn ơi

\(\frac{2011.2010-1}{2009.2011+2010}=\frac{2011.\left(2009+1\right)-1}{2009.2011+2010}\)

\(=\frac{2011.2009+2011-1}{2009.2011+2010}\)

\(=\frac{2011.2009+2010}{2009.2011+2010}\)

\(=1\)

Nhớ k vs kp với mik nhé,mấy man!

đổi k ko

2011×2010-1

2009×2011+2010

\(\frac{2011\cdot2010-1}{2009\cdot2011+2010}=\frac{2011\cdot\left(2009+1\right)-1}{2009\cdot2011+2010}=\frac{2011\cdot2009+2011\cdot1-1}{2009\cdot2011+2010}=\frac{ }{ }\)\(\frac{2011\cdot2009+2011-1}{2009\cdot2011+2010}=\frac{2011\cdot2009+2010}{2009\cdot2011+2010}=1\)

Ta có : 

\(A=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{2009}}+\frac{1}{2^{2010}}\)

\(2A=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2008}}+\frac{1}{2^{2009}}\)

\(2A-A=\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2008}}+\frac{1}{2^{2009}}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{2009}}+\frac{1}{2^{2010}}\right)\)

\(A=1-\frac{1}{2^{2010}}\)

\(A=\frac{2^{2010}-1}{2^{2010}}\)

Vậy \(A=\frac{2^{2010}-1}{2^{2010}}\)

Chúc bạn học tốt 

Ai nhanh mình k !