Question

a1=-1/2 an=-29*1/2 sn=_450 d-? n-?

Answer 1

Sn = (a1+an)2 * n
n =  2Sn/(a1+an) = 2* -450/(-1/2-29*1/2)= 60
d = (an-a1)/(n-1) = (-29*1/2 +1/2)/(60-1) = -14/59