Odpowiedzi

2009-10-12T22:35:28+02:00
Sn = 2a₁ + (n-1)r/2 * n

5100 = 2a₁ + 11 * 50/2 * 12

5100 = 12a₁ + 3300

12a₁ = 1800

a₁ = 150


an = a₁ +(n-1) * r

a₁₂ = 150 + 11 * 50 = 700