x+5/2005 + x+6/2004 + x+7/2003 = -3 
( x+5/2005 + 1 ) + ( x+6/2004 + 1 ) + ( x+7/2003 + 1 ) = 0 
x + 2010 / 2005 + x+2010/2004 + x+2010/2003 = 0 
x+2010 . ( 1/2005 + 1/2004 + 1/2003 ) = 0
=> x + 2010 = 0 
x = -2010 

x+5/2005+x+6/2004+x+7/2003=-3
=>x+5/2005+x+6/2004+x+7/2003+3=0
=>(x+5/2005+1)+(x+6/2004+1)+(x+7/2003+1)=0
=>x+2010/2005+x+2010/2004+x+2010/2003=0
=>x+2010.(1/2005+1/2004+1/2003)=0
=>x+2010=0(Vì 1/2005,1/2004,1/2003 khác 0)
=>x=-2010

x+5/2005 + x+6/2004 + x+7/2003 = -3
Cộng thêm 3 cho 2 vế
Ta có:
(x+5/2005 + x+6/2004 + x+7/2003) + 3 = -3 + 3
( x+5/2005 + 1 ) + ( x+6/2004 + 1 ) + ( x+7/2003 + 1 ) = 0
x+5+2005/2005 + x+6+2004/2004 + x+7+2003/2003 = 0
x+2010/2005 + x+2010/2004 + x+2010/2003 = 0
Nhóm x+2010 ra ngoài làm thừa số chung
x+2010.( 1/2005 + 1/2004 + 1/2003 ) = 0
x+2010 = 0:( 1/2005 + 1/2004 + 1/2003 )
x+2010 = 0
x = 0 - 2010
x = -2010
Vậy x = -2010