Respostas

2013-09-01T13:24:32-03:00
A) a1=? a20=99 r=5 n=20
an= a1+(n-1)r  > 99=a1+(20-1)5 > a1= 99- 19*5 = 99- 95 = 4

b) a21= 17+(21-1)4 = 17+20*4=17+80=97

c) -5005=15+(n-1)(-10) > -5020= -10n+10 > -10n = -5030 > n= 503

d) 20= a1+ (7-1)3 > a1= 20- 6*3 = 20-18 = 2 > {2,5,8,11,14,17,20...}