Question

15 termo da P.A (9,15,...)

an=a1+(n-1)r S=(a1+an).n /2



me ajudem

Answer 1

An = a1 + (n - 1) r

An = 9 + (15-1) 6

An = 9 + 14 x 6

An = 93

Answer 2

Vamos lá 15 termo faça assim:
an = a1+(n-1).r
an=9+(15-1).6
a15=9+14.6
a15=9+84
a15= 93

r = 15-9 = 6
n= 15