Question

first term of a G.P. is 2 common ratio js "r" average og first and 4th term is 28 find "r"

Answer 1

ar^n-1
2r^1-1=
2r^0=1
ar^n-1
2r^3
2(r^3-r^0)=28
r^3-1=14
r^3=15