Question

A soma dos termos da PA (-16,-14,-12,...,84)

Answer 1

a1 = -16
a2 = -14
r = -14 - ( -16) = -14+16 = 2 *****
84 = -16 + ( n-1)2
84 = -16 + 2n - 2
84 = 2n - 18
84 + 18 = 2n
2n = 102
n = 102/2 = 51 ***
Sn = ( -16 + 84)* 51/2
Sn = 68 * 51/2 = 3468/2 = 1734 ****