Question

Вычислить значение суммы

Answer 1

sqrt(1+1/a^2+1/(a+1)^2) = sqrt((a^4+2a^3+3a^2+2a+1)/(a^2*(a+1)^2)) = sqrt((a^2+a+1)^2/(a^2*(a+1)^2)) = (a^2+a+1)/(a(a+1)) = 1+(1/(a(a+1)) 1+ 1/a-1/(a+1)

Значит

sqrt(1 + 1/1^2 + 1/2^2) + sqrt(1 + 1/2^2+1/3^2 ) + ... + sqrt(1 + 1/99^2 + 1/100^2 ) = 99 + (1/1+1/2+...+1/99) - (1/2+1/3+...+1/100) = 99+1-1/100 = 999/100