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1998^2-1997(1998+1)
=1998^2-(1998-1)(1998+1)
=1998^2-(1998^2-1)
=1998^2-1998^2+1
=1
![](https://rs.olm.vn/images/avt/0.png?1311)
=>(x+1/1998+1)+(x+2/1997+1)=(x+3/1996+1)+(x+4/1995+1)
=>x+1999=0
=>x=-1999
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\(\dfrac{x-1}{2006}+\dfrac{x-10}{1997}+\dfrac{x-19}{1988}=3\)
\(\Leftrightarrow\left(\dfrac{x-1}{2006}-1\right)+\left(\dfrac{x-10}{1997}-1\right)+\left(\dfrac{x-19}{1988}-1\right)=0\)
=>x-2007=0
=>x=2007
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Gọi 1997 là A a có
1996=A-1
1998=A+1
\(A^2-\left(A-1\right)\left(A+1\right)\)
\(=A^2-\left(A^2+A-A+1\right)\)
\(=A^2-\left(A^2+1\right)\)
\(=A^2-A^2-1\)
\(=-1\)
1997*1997-1996*1998
(1996+1)*1997-1996*1998
1996*1997+1997-1996*1998
1996*(1997-1998)+1997
1996*(-1)+1997
-1996+1997=1
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bạn sửa đề lại nha.
\(\frac{x-1}{2006}+\frac{x-10}{1997}+\frac{x-19}{1988}=3\)
=>\(\frac{x-1}{2006}+\frac{x-10}{1997}+\frac{x-19}{1988}-3=0\)
=>\(\left(\frac{x-1}{2006}-1\right)+\left(\frac{x-10}{1997}-1\right)+\left(\frac{x-19}{1988}-1\right)=0\)
=>\(\frac{x-1-2006}{2006}+\frac{x-10-1997}{1997}+\frac{x-19-1988}{1988}=0\)
=>\(\frac{x-2007}{2006}+\frac{x-2007}{1997}+\frac{x-2007}{1988}=0\)
=>\(\left(x-2007\right).\left(\frac{1}{2006}+\frac{1}{1997}+\frac{1}{1988}\right)=0\)
Vì \(\frac{1}{2006}+\frac{1}{1997}+\frac{1}{1988}\ne0\)
=>x-2007=0
=>x=2007
7200
1
86 mũ 2 - 14 mũ 2 = 7396 - 196
= 7200
1998 mũ 2 - 1997 . (1998 + 1) = 3992004 - 3992003
= 1
Chúc bạn học tốt!