Question

determine o a20 da PA (-3,-1,1,3,...)

Answer 1

r=-1-(-3)
r=2
a20=-3+19*2
a20=-3+38
a20=35

Answer 2

an=a1+(n-1).r

an=?
a1=-3
r=2
n=20

an= -3+(20-1).2
an= -3+19.2
an= -3+38
an=35

a20=35

Espero ter ajudado (: