Giải thích các bước giải:
a, 9 - x ⋮ x + 2
→ - (x + 2) + 11 ⋮ x + 2
→ 11 ⋮ x + 2
→ x + 2 ∈ Ư(11)
→ x + 2 ∈{ ± 1 ; ±11 }
→ x ∈ {- 1 ; - 3 ; 9 ; - 13}
b, 5 - 2x ⋮ x + 1
→ - 2(x + 1) + 7 ⋮ x + 1
→ 7 ⋮ x + 1
→ x + 1 ∈ Ư(7)
→ x + 1 ∈ {± 1 ; ± 7}
→ x ∈ {0 ; - 2 ; 6 ; - 8}
c, x² + 3x + 2 ⋮ x - 1
→ (x² - 2x + 1) + (5x - 5) + 6 ⋮ x - 1
→ (x - 1)² + 5(x - 1) + 6 ⋮ x - 1
→ (x - 1)(x - 1 + 5) + 6 ⋮ x - 1
→ (x - 1)(x +4)+ 6 ⋮ x - 1
→ 6 ⋮ x - 1
→ x - 1 ∈ Ư(6)
→ x - 1 ∈ {± 1 ; ± 2 ; ± 3 ; ± 6}
→ x ∈ {2 ; 0 ; 3 ; - 1 ; 4 ; - 2 ; 7 ; - 5}