Tìm x, y ∈ Z sao cho: |x+25|+ |-y+5| = 0

Câu 3: Tìm x, y ∈ Z sao cho:

a. |x+25|+ |-y+5| = 0

b. |x-1|+ |x- y+5| ≤ 0

c. xy + 3y – 3x = 1