hơi dài đấy 3
a,
2n+1\(⋮\)2n-3
2n-3+4\(⋮\)2n-3
\(_{\Rightarrow}\)4\(⋮\)2n-3
2n-3\(\in\)Ư(4)=(1;4;2;-1;-4;-2)
2n-3 | 1 | 2 | 4 | -1 | -2 | -4 |
2n | 4 | 5 | 7 | 2 | 1 | -1 |
n | 2 | 1 |
vậy n\(\in\)(2;1)
b;
3n+2\(⋮\)3n-4
3n-4+6\(⋮\)3n-4
=>6\(⋮\)3n-4
3n-4\(\in\)Ư(6)=(1;2;3;6;-1;-2;-3;-6)
3n-4 | 1 | 2 | 3 | 6 | -1 | -2 | -3 | -6 |
3n | 5 | 6 | 7 | 10 | 3 | 2 | 1 | -2 |
n | 3 | 5 | 1 | -1 |
vậy n\(\in\)(3;5;-1;1)