Question

Aflati numarul natural x daca : 3 + 6 + 9 + . . . + 297 = 150x . 

Answer 1

3 + 6 + 9 + . . . + 297 = 150x |:3 (impartim toata ecuatia prin 3)

1+2+3+......+99=50x
Folosim suma lui Gauss n (n+1)/2
99(99+1)/2=99*100/2=99*50

99*50=50*x
x=99