Question

A soma dos termos da P.A. (-16, -14, -12, …, 84) é:

Answer 1

(-16,-14,-12,-10,-8,-6,-4,-2,0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,82,84)

espero ajudar ♥

Answer 2

resolução!

r = a2 - a1

r = - 14 - (-16)

r = 2

an = a1 + ( n - 1 ) r

84 = - 16 + ( n - 1 ) 2

84 = - 16 + 2n - 2

84 = - 18 + 2n

84 + 18 = 2n

102 = 2n

n = 102/2

n = 51

Sn = ( a1 + an ) n / 2

Sn = ( - 16 + 84 ) 51 / 2

Sn = 68 * 51 / 2

Sn = 34 * 51

Sn = 1734