" Life is not a problem to be solved but a reality to be experienced! "
© Copyright 2013 - 2025 KUDO.TIPS - All rights reserved.
S6=57
a)2+15r
45=15r/:15
3=r
S20=4+(20-1)x3x10
S20=610
b)a1=2
a3=2+2x3=8
an=2+(n-1)x3=3n-1
8^2=2(3n-1)
3n-1=32
n=11