vì |x+1,1| >=0
|x+1,2|>=0
|x+1,3|>=0
|x+1,4|>=0
=> |x+1,1|+|x+1,2|+|x+1,3|+|x+1,4| >=0
=> 5x >= 0
mà 5>0
nên x>=0
khi đó |x+1,1|=x+1,1
......................................
|x+1,4|=x+1,4
=> (x+1,1)+(x+1,2)+(x+1,3)+(x+1,4)=5x
4x + (1,1+1,2+1,3+1,4)=5x
5=5x-4x
=> x=5
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