1-2+3-4+5-6...+19-20
AJUTOR VA ROG MULT... CLS 6


Răspuns :

1 -2 + 3 - 4 + 5 -6 +...+ 19 -20 =

= (1 - 2) + (3 -4) + (5-6) +...+ (19 -20) =

= - 1 + (-1) + (-1) +...+ (-1) de 20:2 = 10 ori =

= ( -1 ) × 10 =

= - 10
1 - 2 + 3 - 4 + 5 - 6 + .. + 19 - 20 =

= (1 - 2) + (3 - 4) + (5 - 6) + .. + (19 - 20)

= -1 × 10

= - 10