Question

Tính hợp lí( nếu có thể)

12-12+11+10-9+8-7+5-4+3-2-1

Answer 1

12 - 12 +11 + 10 - 9 + 8 - 7 + 5 - 4 + 3 - 2 - 1

= ( 11 - 1 ) + ( 10 -9 ) + ( 8-7) + ( 5 - 4 ) + ( 3-2  ) 

= 10 + 1 + 1 + 1 + 1

=14

Answer 2

12-12+11+10-9+8-7+5-4+3-2-1

=(12-12)+(11+10)-(9-8)-(7-5)-(4-3)-(2+1)

=0+21-1-2-1-3

=21-(1+2+1+3)

=21-7

=14