Question

Determine o 50° termo da PA (9, 13, 17, 21,....)

Answer 1

a2 - a1 = r
13 - 9 = 4
r = 4

a50 = a1 + (an - 1).r
a50 = 9 + (50- 1) . 4
a50 = 9 + 196
a50 = 205

Answer 2

an = a1 + (n-1) *r

an = 9 +(50-1) * 4

an = 9 +49 * 4

an = 9 + 196

an = 205