👤

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

Răspuns :

110-100=10

..............

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

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

= 1+1+1+...+1 = 1×10 = 10