Question

Determine o decimo oitavo termo da PA (3, 9, 15,...)

Answer 1

a2-a1=r
9-3 = r = 6
an = a1 + (n-1)r
a18= 3 + (18-1)6
a18 = 3+ 17x6
a18 = 105

Answer 2

a2-a1=r
9-3=6
a18=3+17r=> a18= 3 + 17.6= 105