Question

dada a P.A (12,24,36,...,180)calcule a soma de seus termos​

Answer 1

an = a1 + ( n-1) .r

↓

180 = 4 + ( n-1).4

180 = 4 + 12 ( n-4)

180 - 4 + 12 = 4n

180 = 4n

180/4=n

n= 45