Resposta :
3)an=a1+(n-1)r
74=8+(23-1)r
74=8-22r
66:22
r=3
4)an =a1+(n-1)r
a13=a7+6r
6r38-20
6r=18/6
a razao e
r=3
a20=a13+7r
a20=38+7 razao 3
a20+21
a20=59 reposta 59
5)so resposta
n=1 a1 = 3.1-2=1
n=2 a2 =3.2-2=4
n=3=a3 =3.3-2=7
reposta ; (1,4,7)
6) reposta; 73
7)reposta: a5=1000
r=4
a5=a1+4r
1000=a1+16
a1=984 reposta;984