Deret bilangan 100+50+25+.... Tentukan A.suku ke 50 B.jumlah 50 suku pertama

U1 = a = 100
r = u2/u1 = 50/100 = 1/2.

A)  Un = a.r ⁿ⁻¹

     U50 = 100.(1/2) ⁵⁰⁻¹

             = 100.(1/2) ⁵⁰⁻¹

             = 50 ⁴⁹ .

B) Sn = a (1-r ⁿ)/ 1-r
    S50 = 100 (1-1/2 ⁵⁰)/ 1-1/2
    S50 = 100 (1-1/2 ⁵⁰)/ 1/2
    S50 = 100 (1-0)/ 1/2
    S50 = 100 / 1/2
    S50 = 200.