Question

cum se rezolva ex ?repede va rog
(1+2+3+...+100)+(-1-2-3-...-103)

Answer 1

(1+100)*100/2  +  (-1-103)*103/2=
=101*50  + (-104)* 103/2=
=5050 -52*103=
=5050-5356=
= -306

Answer 2

(1+2+3+...+100)+(-1-2-3-...-103)

(1+2+3+...+100)-suma Gauss    S=[n(n+1)]:2=100×101:2=5050


(-1-2-3-...-103) dam factor comun (-1)⇒(1+2+3+...103)dar e tot suma Gauss  S=[n(n+1)]:2

   (1+2+3+...103)=[103×104]:2=5356

(1+2+3+...+100)+(-1-2-3-...-103) =5050-5356=-306