Răspuns:
Explicație pas cu pas:
S = 17 + 18 + 19 + ..... + 50
50 - 17 + 1 = 34 termeni are suma
S = 34 × ( 17 + 50 ) : 2
S = 34 × 67 : 2
S = 17 × 67
S = 1139
____________________________
Sau:
S = (1+2+3+ ....+ 16 + 17 + 18 + 19 + .... + 50 ) - ( 1+2+3+......+16)
S = 50 × ( 1 + 50 ) : 2 - [ 16 × ( 1 + 16 ) : 2 ]
S = 25 × 51 - 8 × 17
S = 17 × ( 25 ×3 - 8 )
S = 17 × 67
S = 1139
