tính \(\frac{2001}{2004}.\frac{1001}{2001}.\frac{2004}{2006}.\frac{2008}{2002}.\frac{2006}{2008}\)
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. là x á nha
=\(\frac{2006}{2008}.\frac{2001}{2004}.\frac{2008}{2002}.\frac{2004}{2006}.\frac{1001}{2001}\)
=\(\frac{2006.2001.2008.2004.1001}{2008.2004.2002.2006.2001}\)
=\(\frac{1001}{2002}\)
= \(\frac{2006\cdot2001\cdot2008\cdot2004\cdot1001}{2008\cdot2004\cdot2002\cdot2006\cdot2001}\)
= \(\frac{1\cdot1\cdot1\cdot1\cdot1001}{1\cdot1\cdot2002\cdot1\cdot1}\)
= \(\frac{1}{2}\)

\(\text{Ta có: }\): \(\frac{2006}{2008}\text{ x }\frac{2001}{2004}\text{ x }\frac{2008}{2002}\text{ x }\frac{2004}{2006}\text{ x }\frac{1001}{2001}\)
\(=\frac{2006\text{ x }\text{ }2001\text{ x }2008\text{ x }2004\text{ x }1001}{2008\text{ x }2004\text{ x }2002\text{ x }2006\text{ x }2001}\text{ }\)
Rút gọn các số ( 2006 ; 2001 ; 2008 ; 2004) ở cả tử và mẫu ta có:
\(=\frac{1001}{2002}=\frac{1}{2}\)
\(\frac{2006}{2008}\times\frac{2001}{2004}\times\frac{2008}{2002}\times\frac{1001}{2001}\)
\(=\frac{2006\times2001\times2008\times1001}{2008\times2004\times2002\times2001}\)
\(=\frac{1001}{2002}=\frac{1}{2}\)

=1+1/2001+1+1/2002+1+1/2003+...+1+1/2008=8+1/2001+1/2002+1/2003+...+1/2008>8
\(\frac{2002}{2001}+\frac{2003}{2002}+\frac{2004}{2003}+\frac{2005}{2004}+\frac{2006}{2005}+\frac{2007}{2006}+\frac{2008}{2007}+\frac{2009}{2008}>8\)

minh lam duoc roi . cach viet phan so ban bam vao o mau vang o cuoi trang .cu di con chuot xuong cuoi trang thi thay 1 o vang , vao xem huong dan la biet ngay ma.

mỗi số hạng trong biểu thức A đều nhỏ hơn 1 mà có 15 số nên tổng A sẽ nhỏ hơn 15
ta thay tong tren <1+1+1+1+1+1+1+1+1+1+1+1+1+1+1
hay tong tren be hon 15

\(\frac{2006}{2008}\times\frac{2001}{2004}\times\frac{2008}{2002}\times\frac{2004}{2006}\times\frac{1001}{2001}=\frac{2006.2001.2008.2004.1001}{2008.2004.2002.2006.2001}\)
\(=\frac{\left(2001.2004.2006.2008.\right).1001}{\left(2001.2004.2006.2008\right).2002}=\frac{1001}{2002}=\frac{1001.1}{1001.2}=\frac{1}{2}\)

=\(\frac{2001x2004x1001x2006}{2004x2006x2001x2002}\)=\(\frac{1}{2}\)
\(=\frac{2001.2004.1001.2002}{2004.2006.2001.2002}=\frac{1.1.1001.1}{1.2006.1.1}=\frac{1001}{2006}\)

Ta có : \(\frac{x^2-2008}{2007}+\frac{x^2-2007}{2006}+\frac{x^2-2006}{2005}=\frac{x^2-2005}{2004}+\frac{x^2-2004}{2003}+\frac{x^2-2003}{2002}\)
=> \(\frac{x^2-2008}{2007}+1+\frac{x^2-2007}{2006}+1+\frac{x^2-2006}{2005}+1=\frac{x^2-2005}{2004}+1+\frac{x^2-2004}{2003}+1+\frac{x^2-2003}{2002}+1\)
=> \(\frac{x^2-2008}{2007}+\frac{2007}{2007}+\frac{x^2-2007}{2006}+\frac{2006}{2006}+\frac{x^2-2006}{2005}+\frac{2005}{2005}=\frac{x^2-2005}{2004}+\frac{2004}{2004}+\frac{x^2-2004}{2003}+\frac{2003}{2003}+\frac{x^2-2003}{2002}+\frac{2002}{2002}\)
=> \(\frac{x^2-1}{2007}+\frac{x^2-1}{2006}+\frac{x^2-1}{2005}=\frac{x^2-1}{2004}+\frac{x^2-1}{2003}+\frac{x^2-1}{2002}\)
=> \(\frac{x^2-1}{2007}+\frac{x^2-1}{2006}+\frac{x^2-1}{2005}-\frac{x^2-1}{2004}-\frac{x^2-1}{2003}-\frac{x^2-1}{2002}=0\)
=> \(\left(x^2-1\right)\left(\frac{1}{2007}+\frac{1}{2006}+\frac{1}{2005}-\frac{1}{2004}-\frac{1}{2003}-\frac{1}{2002}\right)=0\)
=> \(x^2-1=0\)
=> \(x^2=1\)
=> \(x=\pm1\)
Vậy phương trình có 2 nghiệm là x = 1, x = -1 .
\(\dfrac{2001}{2004}\cdot\dfrac{1001}{2001}\cdot\dfrac{2004}{2006}\cdot\dfrac{2008}{2002}\cdot\dfrac{2006}{2008}\)
\(=\dfrac{2001}{2001}\cdot\dfrac{2004}{2004}\cdot\dfrac{2008}{2008}\cdot\dfrac{2006}{2002}\cdot\dfrac{1001}{2006}\)
\(=\dfrac{2006}{2002}\cdot\dfrac{1001}{2006}\)
\(=\dfrac{1001}{2002}=\dfrac{1}{2}\)
`2001/2004 . 1001/2001 . 2004/2006 . 2008/2002 . 2006/2008`
`= (2001 . 1001 . 2004 . 2008 . 2006)/(2004.2001.2006.2002.2008)`
`= (1 . 1 . 1 . 1 . 1)/(1.1.1.2.1)`
`= 1/2`