barisan geometri u3=63 dan u6=1701, maka u4

U3 = ar^2 = 63
U6 = ar^5 = 1701
U6 = ar^2 . r^3 = 1701
U6 = 63 . r^3 = 1701

r^3 = 1701/63
r^3 = 27
r = 3

U4 = ar^2 . r
U4 = 63 . 3
U4 = 189

semoga membantu