Question

calcule a soma dos 100 primeiros termos da PA ( 1, ½ , 0 , … )

Answer 1

r = -1/2
a1 = 1

an=a1+(n-1)r
a100=1+99*(-1/2)
a100=1-99/2
a100=2/2-99/2
a100=-97/2

Sn=n*(a100+a1)/2
S100=100*(-97/2+1)/2
S100=100*(-97/2+2/2)/2
S100=100*(-95/2)/2
S100=50*(-95/2)
S100=25*(-95)
S100=-2375

Espero ter ajudado.