Question

Help !!

Answer 1

`P = 1 + 4/(sqrt x + 1) in ZZ`.

Nếu ` sqrt x in I -> sqrt x + 1 in I -> 4/(sqrt x + 1) in I -> P in I (` Vô lý `)`.

`-> sqrt x in ZZ`.

`-> 4 vdots sqrt x + 1`

`<=> sqrt x + 1 in Ư(4)`

`-> sqrt x + 1 in {+-1, +-2, +-4}`

`-> x in {0, 1, 9}`