Xoá hộ lun ik:>

Sai rồi kìa?

Vì `a,b,c>0` nên \(\dfrac{a}{a+b}<1\)

`=>` \(\dfrac{a}{a+b+c}<\dfrac{a}{a+b}<\dfrac{a+b}{a+b+c}\)

Tương tự 

\(\dfrac{b}{a+b+c}<\dfrac{b}{b+c}<\dfrac{b+c}{a+b+c}\)

\(\dfrac{c}{a+b+c}<\dfrac{c}{c+a}<\dfrac{c+a}{a+b+c}\)

`=>` \(1<\dfrac{a}{a+b}+\dfrac{b}{b+c}+\dfrac{c}{c+a}<2\)

Bn đọc kĩ đề nhé!

`5^{x+2}=625`

`5^{x+2}=5^4`

`=>x+2=4`

`=>x=4-2`

`=>x=2`

Ta có :

`2/3=10/15`

`5/6=10/12`

`=>10/15<10/x<10/12`

`=>x={14;13}`

`[(4x+28)*3+55]:5=35`

`(4x+28)*3+55=7`

`3(4x+28)=-48`

`4x+28=-16`

`4x=-44`

`x=-11`