Show life that you have a thousand reasons to smile
© Copyright 2024 DOKU.TIPS - All rights reserved.
ex . = 1+1+.... +1 = 30
suma de 30 termeni
S = 3° +3¹ +3² + 3³ + ......... + 3³⁰ inmultim cu 3
3S = 3 + 3² + 3³ + 3⁴ + ....... + 3 ³⁰ + 3 ³¹ din care scadem S
S = -1 - 3 - 3² - 3³ - 3⁵ - ....... - 3³⁰
------------------------------------------------------------------
2 · S = 3³¹ - 1
S = ( 3³¹ -1 ) / 2