Question

calcule a soma dos 154 primeiros termos da pa (1;3;5;...)

Answer 1

An = A1 + ( n - 1 ) • r
An = 1 + ( 154 - 1 ) • 2
An = 1 + 153• 2
An = 1 + 306
An = 307

Sn = ( A1 + An ) • n / 2
Sn = ( 1 + 307 ) •154 / 2
Sn = 308 • 154 / 2
Sn = 47432/ 2
Sn = 23716

Answer 2

a1 = 1
a2 = 3
a3 = 5

r = 3 - 1 = 2****
n = 154

a154  = a1 + 153r ou  1 +  153 ( 2)  ou   1 + 306 = 307 ***** ( an)
S154  = ( a1 + a154). 154/2
S154 = ( 1  + 307). 77
S154 = 308 * 77 =23 716 ****