Question

calcule o vigésimo termo da p.a 3/2;11/2

Answer 1

a1 = 3/2
a2 = 11/2

r = 11/2 - 3/2
r = (11-3)/2
r = 8/2
r = 4

n = 20

a20 = ?

an = a1 + (n - 1) . r
a20 = 3/2 + (20 - 1) . 4
a20  = 3/2 + 19 . 4
a20 = 3/2 + 76
a20 = (3 + 152)/2
a20 = 155/2