x+2x+3x+...+100x
calculam suma: (primul+ultimul) x cati termeni sunt (x+100x) x 100
------------------------------------------------- = ------------------------
2 2
101x x 100 10100x
= ------------------ = ------------- = 5050x
2 2
acum rezolvam ecuatia: 5050x=50500
x=50500:5050
x=10
