Question

Geometri berturut-turut U2 = 2 dan U5 = 54
U4 = .. ?
tolong, pakai caranya ya~

Answer 1

54 = a.r^4
2=a.r^1

(coret2)

27=r^3
3=r

subtitusi

54=a.3^4
54=a.81
54/81=a
2/3=a

u4=a.r^n-1
=2/3.3^4-1
=2/3.3^3
=2/3*27
=18