Question

If the 4th and the 9th terms of a geometric progression are 1/3 and 81 respectively, find the
first term.​

Answer 1

Answer:

-47. 8

Step-by-step explanation:

a4=1/3

a+3d=1/3 -(1)

a9=81

a+8d=81

a=81-8d -(2)

put eq2 in 1

a+3d=1/3

81-8d+3d=1/3

81-5d=1/3

-5d=1/3-81

-5d=1-243/3

-5d=-242/3

d=242/15=16.1

A=81-8d = 81-8(16.1)

81-128.8 = -47. 8