2 câu trả lời
1-2+3-4+5-6+7-8+9
= ( 1+9)-( 2+8)+( 3+7)-( 4+6)+5
= 10 - 10 + 10 -10 + 5
= 0 +10 -10 + 5
= 0 + 0 + 5
= 0 + 5
= 5
1-2+3-4+5-6+7-8+9
= ( 1+9)-( 2+8)+( 3+7)-( 4+6)+5
= 10 - 10 + 10 -10 + 5
= 0 +10 -10 + 5
= 0 + 0 + 5
= 0 + 5
= 5