Respostas

2013-06-01T11:05:13-03:00

140 X 12 + 11X8 =

1680 + 88 =

1768 Reais

A melhor resposta!
2013-06-01T11:33:10-03:00

an = a1 + ( n - 1) *r

an = 140 + ( 12 - 1 )*(- 8)

an = 140 + 11 * (-8 )

an = 140 - 88

an = 52

 

Sn = ( a1 + an ) * 12/2

Sn = ( 140 + 52 ) *12/2

Sn = 192 * 12/2

Sn = 2304/2

Sn = 1152

1 5 1