Question

calcule a soma da PA (2,5,...,35)

Answer 1

35= 2+(n-1).3
35= 2+3n-3
35+1= 3n
36= 3n
n= 36/3
n= 12

Sn= (2+35).12/2
Sn= 37.12/2
Sn= 444/2
Sn= 222


Espero ter ajudado!

Answer 2

a1 = 2
a2 = 5
r  = 5 - 2  = 3 ****
an = 35
35 = 2 + ( n - 1)3
35 = 2 + 3n - 3
35 + 3 -  2 = 3n
3n = 36
n = 36/3 = 12 ***
S = ( 2 + 35 ). 6
S = 37 * 6
S = 222****