U3 = 20
ar2 = 20 …. Persamaan 1
U5 =80
ar4 = 80 …. Persamaan 2
Substitusi pers. 1 ke pers. 2
ar4 = 80
ar2 r2 = 80
20r2 = 80
r2 = 4, r = 2
ar2 = 20
a.22 = 20
U3 = 20
ar2 = 20 …. Persamaan 1
U5 =80
ar4 = 80 …. Persamaan 2
Substitusi pers. 1 ke pers. 2
ar4 = 80
ar2 r2 = 80
20r2 = 80
r2 = 4, r = 2
ar2 = 20
a.22 = 20