Question

tìm số nguyên x để: x+2 chia hết x-7

Answer 1

\(x+2⋮x-7\)

=>\(x-7+9⋮x-7\)

=>\(9⋮x-7\)

=>\(x-7\in\left\{1;-1;3;-3;9;-9\right\}\)

=>\(x\in\left\{8;6;10;4;16;-2\right\}\)

Answer 2

Ta có:

x + 2 = x - 7 + 9 

Để (x + 2) ⋮ (x - 7) thì 9 ⋮ (x - 7)

⇒ x - 7 ∈ Ư(9) = {-9; -3; -1; 1; 3; 9}

⇒ x ∈ {-2; 4; 6; 8; 10; 16}