không làm thì đừng nói linh tinh giống mk nha
abcd-abc-ab-a=2086
(1000a+100b+10c+d)-(100a+10b+c)-(10a+b)-a=2086
1000a+100b+10c+d-100a-10b-c-10a-b-a=2086
(1000a-100a-10a-a)+(100b-10b-b)+(10c-c)+d=2086
889a+89b+9c+d=2086
=>a=2;b=3;c=4;d=5
Vậy abcd=2345