Question

Bài 1:

\(\frac{5}{x}+\frac{y}{4}=\frac{1}{8}\)

Bài 2:

a) \(\frac{3n+9}{n-4}\)          b) \(\frac{6n+5}{2n-1}\)

Answer 1

k có yêu cầu thì lm = j

Answer 2

1) \(\frac{5}{x}+\frac{y}{4}=\frac{1}{8}\\ =>\frac{5}{x}+\frac{2y}{8}=\frac{1}{8}\)

Từ đây có thể thấy được x=8 

Ta có : 

\(\frac{5}{8}+\frac{y}{4}=\frac{1}{8}\\ =>\frac{y}{4}=-\frac{3}{8}\\ =>y=-\frac{1}{2}\)

2)

a) \(3n+9⋮n-4\\ =>3\left(n-4\right)+21⋮n-4\\ =>21⋮n-4\)

\(=>n-4\in\text{Ư}\left(21\right)=\left\{1;3;7;21;-1;-3;-7;-21\right\}\\ =>n\in\left\{5;7;11;25;3;1;-3;-17\right\}\)

b) \(6n+5⋮2n-1\\ =>6n-1+6⋮2n-1\\ =>6⋮2n-1\\ =>2x-1\in\text{Ư}\left(6\right)=\left\{1;2;3;6;-1;-2;-3;-6\right\}\)

\(=>2x\in\left\{2;3;4;7;0;-1;-2;-5\right\}\\ =>x\in\left\{1;2;0;-1\right\}\)