Respostas

2014-03-23T15:42:09-03:00
S20 = ?  a1 = 2  , a20 = 10

Sn = ( a1 + an) . n/2

S20 = ( 2 + 10 ) . 20/2
S20 = 12 . 10
S20 = 120
1 4 1