calcule a soma dos 18 termos da PA (1, 4, 7, ...)
Soluções para a tarefa
Resposta:Segue as contas abaixo na explicação
Explicação passo a passo:
1)a1=1,r=a2-a1--->r=4-1--->r=3,n=18,a18=?,S18=?
an=a1+(n-1).r Sn=(a1+an).n/2
a18=1+(18-1).3 S18=(1+52).18/2
a18=1+17.3 S18=53.18/2
a18=1+51 S18=53.9
a18=52 S18=477
2)a1=-7,r=a2-a1--->r=-9-(-7)--->r=-9+7--->r=-2,n=25,a25=?,S25=?
an=a1+(n-1).r Sn=(a1+an).n
a25=-7+(25-1).(-2) S25=[-7+(-55)].25/2
a25=-7+24.(-2) S25=[-7-55].25/2
a25=-7-48 S25=[-62].25/2
a25=-55 S25=[-31].25
S25=-775
3)PA(1,3,....)
a1=1,r=a2-a1--->r=3-1--->r=2,n=27,a27=?,S27=?
an=a1+(n-1).r Sn=(a1+an).n/2
a27=1+(27-1).2 S27=(1+53).27/2
a27=1+26.2 S27=54.27/2
a27=1+52 S27=27.27
a27=53 S27=729
4)a1=3+3+...--->9,an=3+3+....--->54 ou 57,r=3,n=?,Sn=?
Resposta Verdadeiro Desconsidera
an=a1+(n-1).r an=a1+(n-1).r
54=9+(n-1).3 57=9+(n-1).3
54=9+3n-3 57=9+3n-3
54=6+3n 57=6+3n
54-6=6-6+3n 57-6=6-6+3n
48=3n 51=3n
n=48/3 n=51/3
n=16 n=17
Sn=(a1+an).n/2 Sn=(a1+an).n/2
S16=(9+54).16/2 S17=(9+57).17/2
S16=63.16/2 S17=66.17/2
S16=63.8 S17=33.17
S16=504 S17=561
5)a1=690,r=a2-a1--->r=740-690--->r=50,n=15,a15=?,S15=?
an=a1+(n-1).r Sn=(a1+an).n/2
a15=690+(15-1).50 S15=(690+1390).15/2
a15=690+14.50 S15=2080.15/2
a15=690+700 S15=1040.15
a15=1390 reais S15=15600 reais
PA(690,740,790,840,890,940,990,1040,1090,1140,1190,1240,1290,1340,1390)