Đáp án:
`1.`
`|x+1|+|x+2|+|x+3|+|x+4|=10x``(1)`
`VT` $\begin{cases}|x+1| \geq 0 ∀x\\|x+2|\geq 0 ∀x\\|x+3|\geq 0 ∀x\\|x+4|\geq 0 ∀x\end{cases}$
`=> VT>=0 ∀x`
`=> 10x>=0`
`=> x>=0`
`(1)=>x+1+x+2+x+3+x+4=10x`
`=> 4x+10=10x`
`=> 10=10x-4x`
`=> 10=6x => x=5/3`
Vậy `x=5/3`
`2.`
`x=m/(n+2017)=n/(m+2017)=2017/(m+n)`
`=(m+n+2017)/(n+2017+m+2017+m+n)=(m+n+2017)/(2(m+n+2017))=1/2`
Vậy `x=1/2`
