Question

determine o 20°termo da p.a (5,10...

Answer 1

An = A1 + (n - 1) . r
An = 5 + (20 - 1) . 5
An = 5 + 19 . 5
An = 5 + 95
An = 100

Answer 2

.
$a_n=a_{20} \\ a_1=5 \\ n=20 \\ r=10-5=5 \\ \\ a_n=a_1+(n-1)r \\ \\ a_{20}=5+(20-1)5 \\ \\ a_{20}=5+(19)5 \\ \\ a_{20}=5+95 \\ \\ a_{20}=100$