Răspuns :
S = 5 + 10 + 15 + ... + 150 suma , are 30 de termeni !
S =150+ 145 + 140 + ... + 5
_____________________________ le adunam ...
2S=155+ 155+ 155 + ... + 155 = 155 × 30 = 4650
S = 4650 : 2 = 2325
S =150+ 145 + 140 + ... + 5
_____________________________ le adunam ...
2S=155+ 155+ 155 + ... + 155 = 155 × 30 = 4650
S = 4650 : 2 = 2325