(a_4=54), (a_9=13122)
[ ar^3=54,\quad ar^8=13122 ] [ r^5=\dfrac{13122}{54}=243=3^5\implies r=3 ] [ a\cdot27=54\implies a=2 ]
G.P.: (2,6,18,54,\ldots)
General term: (a_n=2\cdot3^{n-1})
Answer: (2,6,18,\ldots);\ (a_n=2\cdot3^{n-1})
(a_4=54), (a_9=13122)
[ ar^3=54,\quad ar^8=13122 ] [ r^5=\dfrac{13122}{54}=243=3^5\implies r=3 ] [ a\cdot27=54\implies a=2 ]
G.P.: (2,6,18,54,\ldots)
General term: (a_n=2\cdot3^{n-1})
Answer: (2,6,18,\ldots);\ (a_n=2\cdot3^{n-1})