Question

Determinar a soma dos trinta primeiros termos da P.A (-4,-2,0,4,6,...).

Answer 1

an = a₁ + (n - 1) r

an = - 4 + ( 30 -1) 2

an = 54

-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

- 4 - 2 = -6
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 = 756

-6 + 756 = 750  -------------- resposta