Răspuns:
Explicație pas cu pas:
Primul mod:
( 1 + 2 + 3 + ...... + 94 + 95 + .....+ 304 ) - ( 1 + 2 + 3 + ..... + 94 ) =
= 304 × (1+304) : 2 - [ 94 × ( 1 + 94 ) : 2 ] =
= 152 × 305 - ( 47 × 95 ) =
= 46 360 - 4 465 =
= 41 895
______________________________________________
Al doilea mod:
95 + 96 + 97 + ..... + 304 = 41 895
304 - 95 + 1 = 210 termeni are suma
= 210 × ( 95 + 304 ) : 2 =
= 105 × 399 =
= 41 895
95 + 96 + 97 + ... + 304 =
[ ( 304 - 95 + 1 ) × ( 95 + 304 ) ] : 2 =
[ ( 209 + 1 ) × 399 ] : 2 =
( 210 × 399 ) : 2 =
83790 : 2 = 41895
