Jawabanmu

2014-02-16T19:45:08+07:00
A =1 , b = 2 , Un = a+(n-1)b = 1+(n-1)2 =1+2n-2= 2n-1
U8 = 1+(8-1)2=15
U10 = 1+(10-1)2=19
10.240 = 1+(n-1)2
10.240 = 2n-1
10.240+1=2n
10.241=2n
n= 10.241/2