Question

cât fac 99+2 (1+2+3+...+x)=99la patrat

Answer 1

Ok, duci 99 in partea cealalta a ecuatiei, obtii: 2*(1 + 2 + ... + x) = 99*99 - 99 In partea stinga observam ca putem aplica suma lui Gauss, iar in dreapta scoatem 99 in fata: 2* x*(x+1)/2 = 99*(99-1) => x*(x+1)= 99*98 => x = 98