Question

bài 7,8,9,10 nha ạ

bài 7 ,8 ,9,10 nha ạ

Answer 1

`#3107.101107`

`7.`

`x = (a - 2)/5` 

Để x nguyên:

`=> (a - 2) \in \text{B(5)}`

`=> (a - 2) \in {5; 10; 15;...}`

`=> a \in {7; 12; 17;...}`

`8.`

`x = (a - 5)/a`

`=> x = a/a - 5/a = 1 - 5/a`

Để x nguyên `=> a \in \text{Ư(5)}`

`=> a \in {+-1; +-5}.`

Answer 2

9. Với \(x\ne2\):

\(A=\dfrac{x+1}{x-2}=\dfrac{x-2+3}{x-2}=1+\dfrac{3}{x-2}\)

Để A nguyên thì \(\dfrac{3}{x-2}\) nguyên \(\Rightarrow\left(x-2\right)\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\Rightarrow x\in\left\{-1;1;3;5\right\}\)

10. Với \(x\ne-5:\)

\(B=\dfrac{2x-1}{x+5}=\dfrac{2x+10-11}{x+5}=2-\dfrac{11}{x+5}\)

Để B nguyên thì \(\dfrac{11}{x+5}\) nguyên \(\Rightarrow\left(x+5\right)\inƯ\left(11\right)=\left\{-1;1;11;-11\right\}\Rightarrow x\in\left\{-6;-4;6;-16\right\}\)