x+1/2=8/x+1 x:(9 1/2-3/2)=0.4+2/9-2/11/1.6+8/9-8/11

`a ) (x + 1)/2 = 8/(x + 1)`

`=> (x+1).(x+1) = 2.8`

`=> (x+1)^2 = 16`

`=>`$\left[ \begin{array}{l}(x+1)^2 = 4^2\\(x+1)^2 = (-4)^2\end{array} \right.$ 

`=>`$\left[ \begin{array}{l}x + 1 = 4\\x + 1 = -4\end{array} \right.$ 

`=>`$\left[ \begin{array}{l}x = 3\\x = -5\end{array} \right.$ 

Vậy `x ∈ {3 ; -5}`

`b ) x : (9 1/2 - 3/2 ) = 0,4 + 2/9 - 2/11 . 1/6 + 8/9 - 8/11`

`=> x : ( 19/2 - 3/2 ) = 28/45 - 1/33 + 8/9 - 8/11`

`=> x : 8 = 293/495 + 8/9 - 8/11`

`=> x : 8 = 733/495 - 8/11`

`=> x : 8 = 373/495`

`=> x = 373/495 .8`

`=> x = 2984/495`

Vậy `x = 2984/495`

`---`

`x : ( 9 1/2 - 3/2 ) = (0,4 + 2/9 - 2/11 )/(1,6 + 8/9 - 8/11 )`

`=> x : (19/2 - 3/2 ) = (2 . (1/5 + 1/9 - 1/11))/(8.(1/5 + 1/9 - 1/11))`

`=> x : 8 = 2/8`

`=> x = 2/8 .8`

`=> x = 2`

Vậy `x = 2`

`#dtkc`

Đáp án+Giải thích các bước giải:

`frac{x+1}{2}=frac{8}{x+1}`

 `⇒(x+1)^{2}=2.8`

`⇒(x+1)^{2}=16`

`⇒(x+1)^{2}=4^{2}`

`⇒x+1=4`

`x=4-1=3`

$Hoặc:$

`⇒(x+1)^{2}=(-4)^{2}`

`⇒x+1=−4`

`x=-4-1=-5`

$Vậy:$ `x ∈{3;−5}`

`x:(9frac{1}{2}−frac{3}{2})=frac{0,4+frac{2}{9}−frac{2}{11}}{1,6+frac{8}{9}−frac{8}{11}`

`x:(frac{19}{2}−frac{3}{2))=frac{2.(frac{1}{5}+frac{1}{9}−frac{1}{11})}{8.(frac{1}{5}+frac{1}{9}−frac{1}{11})`

`x:8=frac{2}{8}`

`x=frac{2}{8}.8=frac{2}{8}.frac{8}{1}=2`

$Vậy:$ `x=2`

${\color{cyan}{\textit{#Kakashi}}}$