Question

Tentukan banyak bilangan antara 7 sampai 800 yang habis dibagi 3

Answer 1

U1 = 9
Un = 798
b = 3

798 = 9 + (n-1)3
789 = 3n -3
786 = 3n
n = 262

Sn = n/2 (a + Un)
S262 = 262/2 (9 + 798)
         = 161. 807
         = 129.927

Answer 2

9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63,66,69,72,75,78,81,84,87,90,93,96,99,102,105,108,111,114,117,120,123,126,129,132,135,138,141,144,147,150,153,156,159,162,165,168,171,174,177,180,183,186,189,192,195,198,....dst
tinggal ditambahkan tiga aja