Question

Determine o 61 termo da P.a (9,13,17,21,...)

Answer 1

n2-n1=r
13-9=4

An= A1+(n-1).r
A61=9+(61-1).4
A61=9+60.4
A61= 9+240
A61= 249

Answer 2

(9,13,17,21,...) a1 = 9 r = 5 an = a1+(n-1) x r a61 = 9 + (61-1) x 5 a61 = 9+ 60 x 5 a61 = 309